FY1996 Progress – FY1997 Plans

 

COOPERATIVE INSTITUTE FOR MESOSCALE METEOROLOGICAL STUDIES
THE UNIVERSITY OF OKLAHOMA

Annual Report
FY 1996 Progress/FY 1997 Plans

Peter J. Lamb, Director
Randy A. Peppler, Associate Director

INTRODUCTION

The University of Oklahoma (OU) and NOAA established the Cooperative Institute for Mesoscale Meteorological Studies (CIMMS) in 1978 to promote cooperation and collaboration on problems of mutual interest among research scientists in the NOAA Environmental Research Laboratories (ERL), mainly the National Severe Storms Laboratory (NSSL), and faculty, postdoctoral scientists, and students in the School of Meteorology and other academic departments at OU. The Memorandum of Agreement (MOA) between OU and NOAA was updated in 1995 to include the National Weather Service (NWS), expanding the formal OU collaboration to the Operational Support Facility (OSF) of the NEXRAD Program, the new NCEP (National Centers for Environmental Prediction) Storm Prediction Center (SPC), and the NWS Forecast Office, all located in Norman, Oklahoma. Through CIMMS, OU faculty and ERL/NWS scientists also collaborate on research supported by other NOAA programs and laboratories as well as other agencies such as the National Science Foundation (NSF), the U.S. Department of Energy, the Federal Aviation Administration (FAA), and the National Aeronautics and Space Administration (NASA).

A new 5-year cooperative agreement between OU and NOAA for CIMMS funding took effect on July 1, 1996. Under this agreement, CIMMS concentrates its efforts and resources on five principal research themes, the fifth of which is new under the current plan: (1) basic convective and mesoscale research, (2) forecast improvements, (3) climate effects of/controls on mesoscale processes, (4) socioeconomic effects of mesoscale weather systems and regional-scale climate variations, and (5) Doppler weather radar research and development.

This report covers research progress for the period July 1, 1995, through June 30, 1996 (part of the last 3-year plan, now expired), and research plans for the period July 1, 1996, through June 30, 1997 (part of the new 5-year plan).

BASIC CONVECTIVE AND MESOSCALE RESEARCH

Progress – FY 96

Doppler Weather Radar Level II Data Archive

Archival of Level II NEXRAD data tapes continued during FY 96. The original Exabyte tapes, made at the NEXRAD field locations, are stored at OU after being copied at the primary archive, located at the National Climatic Data Center in Asheville, NC. Through the end of FY 96, nearly 18,000 tapes had been archived at OU, with the oldest tapes dating back to mid-1993.

Data Assimilation

Effort has been made on improving previously developed Lagrangian advective schemes to estimate large-scale vorticity using VAD products and reflectivity. A graduate student in the OU School of Meteorology performed code development work.

New additional techniques were developed to improve the simple adjoint (SA) method and least square (LS) method for retrieving low-altitude winds from single-Doppler scans. One promising new technique is to use truncated empirical orthogonal functions to filter noise caused by data errors and/or data holes. This idea is being incorporated into the SA and SL methods.

The classic adjoint method has been successful in meteorological data assimilation with a variety of dynamic models, but is not applicable to physical processes that contain parameterized discontinuities. The problem has become acute in recent years, as much attention in adjoint data assimilation work has turned to physical processes (especially in the storm-scale). To attempt to solve this problem, work began on a generalized adjoint method.

Mesoscale Dynamics

A two-dimensional viscous semigeostrophic eddy wave model was developed and used to study the evolution of fronts and nonlinear saturation of baroclinic instability in terms of balanced mesoscale dynamics. Two types of mathematically admissible surface boundary conditions were derived to represent two types of physical surface conditions: free-slip and non-slip. Numerical simulations were performed to examine how these boundary conditions control the surface flux of the potential vorticity (PV) of the balanced flow and, thus, affect the evolution of PV anomalies in the vicinity of the front. It was found that the long-term evolution of the front is characterized by nonlinear oscillations in association with nonlinear saturation of baroclinic instability, and the related nonlinear processes and their quasi-equilibration are strongly affected by the surface conditions.

Plans – FY 97

Doppler Weather Radar Level II Data Archive

A closeout of the OU archive will be performed, with all original Level II tapes shipped to NCDC for permanent archive.

Storm Scale Data Assimilation

Doppler radar winds and thermodynamic fields retrieved by the SA method will be used to improve mesoscale analysis and prediction. As proof of concept, selected case studies will be performed.

The SA method will be improved for single-Doppler wind retrievals and its codes will be incorporated into the existing mesoscale data assimilation system.

Further development of generalized adjoint computational schemes for parameterized physical processes with discontinuous on/off switches will be attempted.

Dynamic Feedbacks on Deep Convection

An investigation will be initiated to study the feedbacks between vegetation, soil moisture, and the life cycles of deep convection and mesoscale convective systems over the U.S. Southern Great Plains, with a focus on the GEWEX-GCIP GIST domain.

FORECAST IMPROVEMENTS

Progress – FY 96

Data Services provided by the Oklahoma Mesonetwork

This grant supports the FY 1996 maintenance and operation of the Oklahoma Mesonetwork in return for reliable data services. Services include greater than 98% real-time data availability and over 99.9% availability of research-quality archived data. NWS data users for FY1996 were Weather Forecast Offices in Norman, Tulsa, Amarillo, Dodge City, Wichita, and Shreveport, the Storm Prediction Center (formerly the NSSFC), and the Arkansas-Red River Basin River Forecast Center in Tulsa. The Mesonet data are used frequently in short term nowcasts as evidenced by numerous references to the Mesonet in various “State Forecast discussions”. In addition, case studies using the data serve as important training tools on which to improve NWS operations. The data will continue to impact the NWS as it continues its modernization program, especially in the areas of hydrometeorology and radar rainfall calibrations.

Surface Rainfall and Improved River Forecasting

Activities involving the hydrologic modeling group in this grant included the following: providing training sessions to the Tulsa River Forecast Center, setting up hydrologic databases for the Tahlequah basin of the Illinois River, and continuing the development of infiltration parameters for the entire Arkansas-Red River Basin. Activities involving the radar/raingauge calibration group included the following: researching the impact of calibrated radar estimates of rainfall on Quantitative Precipitation Forecasts (QPFs), studying the effect those estimates have on the stream-flow hydrograph produced by hydrologic models, writing a tutorial to document the software that supports this hydrometeorological analysis and forecast system, calibrating WSR-88D precipitation data using raingauge observations from the Oklahoma Mesonet, and working to determine the biases of the WSR-88D radar rainfall estimates.

The Schools of the Pacific Rainfall Climate Experiment (SPaRCE) Project

A pilot program was completed that established a network of raingauges at educational institutions in Pacific island and atoll nations. Students were responsible for properly siting the raingauges and maintaining a continuous daily rainfall record at their site. The goals of this pilot program were to establish the network of raingauges and establish ties with local government weather forecasting and educational organizations. This work, successfully completed, has created the infrastructure for the continuation and enhancement of the project, known as SPaRCE (see Plans – FY 97 below).

Hourly GCIP Precipitation Data Derived from WSR-88Ds Using Raingauge Measurements as the Baseline Data

The validation of hydrologic models that will be developed for GCIP will depend, to a significant degree, on the accuracy of precipitation data, since precipitation is the largest component of the water cycle. Two means of measuring precipitation are raingauges and radar, and both are susceptible to errors in observation. A three-year study was undertaken to assess the accuracy (bias and error variance) of hourly rainfall as estimated by WSR-88D NEXRAD radars. The reference data sets for determining this accuracy are from a network of raingauges in Oklahoma. An important goal of the research is to determine the effect of wind on undercatch for raingauges used in building the reference data set and the effect of sampling error on the validation process. A raingauge testbed was constructed to investigate the undercatch problem. Part of the effort to facilitate this research includes the establishment of the Environmental Verification and Analysis Center (EVAC), which collaborates closely with GCIP in developing and applying statistical averaging techniques designed to minimize the error arising from incomplete spatial sampling and field inhomogeneities. EVAC will allow scientists the opportunity to obtain quality assessments concerning the accuracy of remotely sensed variables and model output. It will also allow for two-way data exchange to enhance the quality of the GCIP database and access to data by research scientists.

The raingauge testbed was constructed and is in place. Two papers were published during 1995 in refereed journals that treated geostatistical technique development for future application to data collected by this project. EVAC itself was established and through it rainfall data from the Oklahoma Mesonetwork and the Agricultural Research Station (ARS) Little Washita network in Oklahoma have been archived.

Plans – FY 97

SPC – Physical Process Studies; Forecast Tool Development and Performance

Physical process studies on mesoscale/synoptic scale systems that cause extreme and severe weather events may be initiated, particularly with respect to hazardous events that evolve into other types of hazardous events and on systems involving multiple hazardous weather elements. Forecast tool development will include the conversion of current meteorological research results into software programs and scripts that will serve as tools on the N-AWIPS workstations. These forecast tools will also be used in the preparation of severe weather products and the new Hazardous Weather Update. Plans also include the development of a verification program that can be used by the SPC to verify all forecast products.

OSF – Focus on Integrated Remote Sensing Technologies Training (FIRSTT)

NWS has requirements for new integrated-remote-sensor applications and training for its new workstations, called AWIPS. The OSF‚s Operations Training Branch (OTB) will help to meet the requirement by changing its mission and name to Focus on Integrated Remote Sensing Technologies Training (FIRSTT). New personnel are beginning work on the development of radar and satellite remote sensing applications. Once these applications are finalized in early 1997, the process of constructing distance-learning training modules will begin, which will be used to instruct the entire NWS workforce on the new applications.

COMET Outreach

Though in the embryonic stages of development, COMET activities related to the SPC mission of forecasting winter and convective storms may be undertaken during this FY.

Developing and Evaluating Forecast Techniques for Hazardous Weather

Work may begin on evaluation of observed hazardous weather phenomena to diagnose and understand their physical processes, in order to develop operational forecasting techniques that would assist forecasters.

Use of Lightning Data in Diagnosing Storm Evolution and Hazards

Data analysis is beginning to examine relationships between trends in lightning ground flash type and rates and trends in storm evolution and hazards. Data from 24 storm days in Oklahoma, Texas and Kansas have been prepared for trend analyses. This work complements a recently completed NSSL analysis of lightning/storm relationships for Arizona storms.

Short-Term Forecasting and Warning of Severe Weather Using Satellite and Radar Data

A study investigating short-term diagnosis and prediction of mesoscale convective systems (MCSs) using multiple sensors will develop algorithm techniques to integrate data from the sensors to characterize MCSs during their entire life cycle. Although studies have improved our understanding of the MCS evolution depicted by one type of sensor, or by some combination of two sensors, little has been done to integrate the available information from all relevant observing systems. Plans are to integrate digital satellite data, WSR-88D Level II data, profiler data, surface data, and lightning ground-strike data. Techniques developed by this project will assist both the NWS SPC in producing operational guidance and NWS forecast offices in nowcasting precipitation and floods.

Long-Term Forecasts Using Severe Weather Climatologies

Work may be initiated to evaluate observed hazardous weather phenomena to diagnose and understand their physical processes, and develop operational forecast techniques that would assist forecasters in predicting such hazardous events.

The Schools of the Pacific Rainfall Climate Experiment (SPaRCE) Project

The one-year pilot study described above will be enhanced into a full project. SPaRCE is a cooperative rainfall climate field project involving high school and college level teachers and students from various Pacific Ocean island and atoll nations. The goals of the project are both research and education oriented. SPaRCE provides participants with videotaped lectures describing various topics relating to rainfall and climate, instrumentation, and instrument siting. Standard raingauges are distributed to the various sites (two per site). Students are responsible for properly siting the raingauges and maintaining a continuous daily rainfall record at their site. The interactive sessions with the participants follow the distribution of each videotaped lecture using the PEACESAT satellite radio communication system. Efforts are being made to seek funding to include schools from Oklahoma and Hawaii. During the next two years, SPaRCE will be incorporated into the Environmental Verification and Analysis Center (EVAC). EVAC will facilitate the storage, analysis, and data dissemination of the SPaRCE data. A World Wide Web Page describing EVAC will be constructed and will incorporate a detailed description of the SPaRCE Program.

Hourly GCIP Precipitation Data Derived from WSR-88Ds Using Raingauge Measurements as the Baseline Data

Plans include bringing together NOAA and NASA scientists interested in the validation of computer models and/or remote sensing algorithms using EVAC as a catalyst. Ongoing and planned tasks include raingauge data quality assessments; applying universal kriging to the selected raingauge networks for various spatial scales using a climatological covariance estimator; comparing error statistics associated with simple averaging and universal kriging; and developing a data set containing volume estimates at different scales computed from the most accurate averaging method and incorporate the data set into the EVAC for access by the GCIP Data Archive Center.

CLIMATIC EFFECTS OF/CONTROLS ON MESOSCALE PROCESSES

Progress – FY 96

Investigations of the Mechanisms of Precipitation Variability in Central and Eastern North America

Research has been conducted in several areas:

Observed Nonlinearities of Monthly Teleconnections between tropical Pacific Sea Surface Temperature Anomalies and central and eastern North American Precipitation

Most investigations of relationships between tropical Pacific sea surface temperature anomaly (SSTA) events and regional climate patterns have assumed the teleconnections to be linear, whereby the climate patterns associated with cold SSTA events are considered to be similar in structure and morphology but opposite in sign to those linked to warm SSTA events. In contrast, and motivated by early evidence of nonlinearity in the above regard, this study identified characteristic (i.e., composite) calendar monthly central and eastern North American precipitation patterns separately for warm and cold SSTA events in different regions of the tropical Pacific (central, eastern, west-central “horseshoe”, far western) identified through principal component analysis. The precipitation anomaly patterns were computed from an approximately 1°-latitude/longitude set of monthly station data for 1950-92. Their robustness and nonlinearity were established using local, regional, and field statistical tests and a variance analysis. This combination of unique SSTA analyses, resulting composite selection and characteristic precipitation anomaly determination from a fine resolution data set increased our understanding of tropical Pacific-North American precipitation teleconnections in several respects. First, significant linkages to the two SSTA modes related to traditional warm and cold events (central and eastern tropical Pacific) were identified for all months except September and October, with all exhibiting some nonlinear characteristics. Conversely, several regions/seasons were confirmed to have essentially linear associations with traditional warm and cold events. However, only nonlinear precipitation teleconnections were associated with SSTAs in tropical Pacific regions largely unrelated to ENSO. The results also demonstrated the sensitivity of central and eastern North American precipitation teleconnections to the location and extent of tropical Pacific SSTAs.

Role of Local Evapotranspiration for Growing Season Precipitation and Crop Yields over the Midwestern United States

Land-atmosphere interactions are central to the natural environment, involving and affecting individual weather systems, regional climate, the hydrological cycle, soil and vegetation status, and agricultural production. This importance is manifest in several long-term, international, biological and geophysical programs, including the Global Energy and Water Cycle Experiment (GEWEX) of the World Climate Research Programme. The first major GEWEX activity, the GEWEX Continental International Project (GCIP) is focusing on the land-atmosphere interactions of the greater Mississippi River basin during the second half of this decade. A land-atmosphere interaction suite of pervasive environmental importance involves the classical issue of the relative contributions to regional precipitation of locally evapotranspired (i.e., recycled) moisture versus externally advected atmospheric water vapor. Using a new but simple formulation, we obtained the first comprehensive estimation of the intraseasonal and interannual variability of those moisture sources for the growing season precipitation of arguably the World’s most productive, largely unirrigated, agricultural region — the Corn Belt and surrounding areas of the Midwestern United States — which also occupies ~35% of the GCIP domain. Consistent with its GCIP co-location, this region is considered representative of the mid-latitude, mid-continent, land-atmosphere interactions that are vital for global water resources and hence food production. For four highly contrasting growing seasons, we found the contribution of the locally evapotranspired moisture to this precipitation to be relatively small and remarkably consistent (largely 19-24%) on a monthly and seasonal mean basis, despite large precipitation and crop yield variations, and to decrease markedly (from a 28% to 15% average) with increasing precipitation on a daily basis. Our approach and results yielded considerable physical insight into the complex land-atmosphere interactions involved, including into plant behavior and the apparent paradox between the above monthly/seasonal and daily time-scale results.

Large-Scale Atmospheric Moisture Field over the Midwestern United States in Relation to Summer Precipitation — Relation between Moisture Budget Components on Different Time-Scales

The moisture budget components and related parameters were evaluated for a large area (about 10**6 km**2) in the Midwestern United States for all 24-hour (12-12 UT) periods during the highly (contrasting) May-August periods of 1975, 1976, 1979, and 1988. First stratifying them in different ways, and then using linear correlation and cross-spectral analysis obtained relationships among the budget components. The results showed that the calculation of evaporation as a residual of the moisture budget equation yielded values close to the (few) existing observations, especially for periods on the order of one month or longer. The evaporation showed a clear bimodal distribution with respect to precipitation, with high evaporation associated with low and high precipitation amounts, and with a minimum of 3.1 mm d-1 for a precipitation rate of about 4-5 mm d-1. The interannual and intraseasonal variations in precipitation were mostly accounted for by the fluctuations of the moisture flux divergence (and chiefly by its velocity divergence component). An extremely high negative correlation (in the 24-hour moisture budget) was found between the horizontal moisture advection and the time change of precipitable water. A high correlation was also found between rainfall and the vertically integrated vertical moist advection. Rainfall and total precipitable water were also positively correlated. In addition there is a low, but significant positive correlation between precipitation and horizontal advection and a negative correlation between precipitation and the time change of precipitable water. Precipitation was found to be correlated with evaporation on a monthly time scale (but not on shorter time scales) indicating a possible feedback between the two variables on that time scale. Power spectrum analysis of the 12-hour moisture budget components revealed peaks in three major frequency bands, located at 2-4, 5-6, and 8-12 days. Several pairs of budget terms exhibited a high coherence squared with a nearly constant phase difference within a broad frequency band in all four summers. The most outstanding results were that maximum precipitation follows the maximum horizontal convergence term by 15 degrees and the moist advection maximum by 120 degrees. Another finding was that the time change of precipitable water and moist advection have a very high coherence squared, and are in-phase over a wide frequency band. Finally, the maximum in precipitation follows maximum precipitable water by about 20 degrees and the maximum time change of precipitable water by 110 degrees.

Studies of the Interannual Variability of the North Atlantic Oscillation and Moroccan Precipitation

The objective of this ongoing project is to use the interannual and intraseasonal variability of the North Atlantic Oscillation (NAO) to develop a seasonal precipitation prediction capability for Morocco. Substantial progress occurred during the past year. This included the construction of a research-quality monthly precipitation data set for Morocco for 1932-present, the advanced statistical analysis of those data that yielded a regionalization of Morocco for precipitation monitoring and prediction, and an intensive inquiry into the optimum characterization and seasonal behavior of the NAO. The latter resulted in the discovery of a pronounced intraseasonal oscillation of the NAO that strongly characterizes the 4-6 months before mid-winter NAO extremes. This effort has laid the foundation for the preparation of “Experimental Precipitation Prediction Statements” for Morocco that will be issued for the first time during the upcoming 1996-97 (winter) rainy season.

Theoretical and Observational Study of the Aerosol Effects on the Marine Stratiform Clouds Radiative Properties and Precipitation Efficiency

Research has been conducted in several areas:

Model Validation Program

Simulations based on the CIMMS 3-D LES cloud model with explicit microphysics have been performed using observations of stratocumulus cloud layers. The results of the study have been published in the Journal of Atmospheric Sciences by Kogan et al. (1995). Based on the model validation study, a new more accurate and computationally efficient numerical technique for calculation of the nucleation and growth of aerosols (Liu et al. 1995; Liu et al. 1996) has been developed. Another validation study based on sets of both microphysical and radiation measurements has been completed and is submitted for publication to the Journal of Atmospheric Sciences in August 1996 (Khairoutdinov and Kogan, 1996). The validation study showed very convincingly that the model’s predicted parameters, including microphysical and radiative, were in good agreement with observations. The study is part of the Ph.D. thesis work conducted by two OU students (Q. Liu and M. Khairoutdinov).

Observational Data Analysis

We analyzed data from the Atlantic Stratocumulus Transition Experiment (ASTEX) and from the Monterey Area Ship Track (MAST) field program. The study resulted in the development of an empirical model of a specific stratocumulus-topped well-mixed boundary layer. The empirical model consists of a comprehensive integrated set of dynamical, turbulence, microphysical (including aerosol and cloud drop spectra), and radiative parameters of the boundary layer and provide an opportunity for very accurate verification of LES model predictions of microphysical and radiative parameters. The study was the basis for the MS thesis work performed by OU student David Lam.

Evaluation of the Aerosol Indirect Effect

The results of the model validation program provided the foundation for the research on aerosol climatic effects. We have evaluated the global distribution of the anthropogenic sulfate aerosol indirect forcing using the stratocumulus cloud climatology data, the sulfate aerosol distributions from a 3-D chemical transport model of Langner and Rodhe, and the parameterization of stratocumulus cloud albedo susceptibility developed using the CIMMS LES model. In addition to the annual estimate of the indirect forcing, its seasonal cycle for each hemisphere and contributions from various factors was also evaluated (Z. Kogan et al, 1996).

Study of the Ship Track Phenomena

The importance of atmospheric aerosol particles is clearly illustrated by studies showing the apparent sensitivity of marine stratocumulus cloud layers to the anthropogenic addition of heat, smoke, and water vapor by ship passages. We conducted a series of large eddy simulations to study the ship track formation under ambient conditions representing different boundary layer thermodynamical structures. We found that ship tracks last longer in the clean marine boundary layer compared to that in the polluted environment. Model results support the assumption of drizzle suppression in the clean environment. However, the liquid water content inside the ship track may be lower or higher than the liquid water content outside the ship track, depending on the specific characteristics of the boundary layer such as the mixed layer height, stability of the boundary layer, as well as the CCN concentration of the environment (Liu et al. 1996). The results of the study are summarized in two papers submitted for publication in a special issue of the Journal of Atmospheric Sciences.

Study of Aerosol Processing using LES Explicit Microphysical Model with the Aerosol Tracking Option

We have developed a new version of the CIMMS LES model that is capable of tracking the aerosol transformations as a result of aerosol nucleation and cloud drop coagulation. The cloud microphysical processes are formulated based on a two-dimensional distribution function that depends on the cloud drop size and the aerosol soluble mass inside each drop. This new feature allows us to study the aerosol history and transformation of the aerosol spectra as a result of cloud drop collisions, nucleation, and scavenging effects. The 3-D simulation of aerosol processing in a stratocumulus cloud-topped boundary layer has demonstrated the effect of coalescence on the transformation of the aerosol spectra inside cloud drops and on the ambient aerosols (Liu and Kogan, 1996).

Simulation of Ice Production Processes

A 3-D model that explicitly formulates both ice and liquid phase microphysics has been developed and verified in a case study of New Mexican summertime cumulus clouds. The model reproduces well the observed cloud in terms of cloud geometry, liquid water content, and concentrations of cloud drops and ice particles. Under simulated conditions, the Hallet-Mossop process is shown to be able to produce ice crystals in concentrations of order 100 L-1 in about 10 minutes. Comparison with the observations suggests that the secondary ice crystal production is indeed the most likely explanation for the large ice particle concentrations found in small New Mexican summertime cumulus. The study is part of the Ph.D. thesis work conducted by the OU student M. Ovtchinnikov.

Atmospheric Radiation Measurement (ARM) Program Research

The ARM Program’s Energy Balance Bowen Ratio (EBBR) data acquisition system measures near-surface winds, vertical gradients of temperature and vapor pressure, and surface net radiation. Using these measurements, two conventional methods are available for computing the surface fluxes of sensible and latent heat — the Profile method and the Bowen Ratio Energy Balance (BREB) method. Since neither method uses the complete information provided by the EBBR, a variational method was developed to combine the merits of the two methods. This method was further improved to include the contributions of multiple scale motions in the planetary boundary layer.

ARM/GCIP Measurements of Soil Moisture and Temperature Profiles at the ARM Southern Great Plains Site

The goal of this effort is to deploy a rugged, automated, and affordable soil water sensor at the surface flux stations of the ARM Southern Great Plains Site, in an attempt to meet the soil water data needs of ARM and GEWEX/GCIP investigators. Various factors required that a different approach from traditional efforts within the soil science or hydrologic communities be devised, requiring choosing the best currently available sensor given logistical and fiscal constraints, implementing a plan, and seeing if it worked. The advice of soil scientists and hydrologists associated with two other research networks in Oklahoma (USDA/ARS Little Washita Micronet; Oklahoma Mesonetwork) was sought, and an engineer/soil scientist possessing extensive experience with weighing lysimeters and other relevant instruments was hired. The implementation effort is ahead of schedule, and the results to date have been very encouraging. The original work plan has been closely adhered to, though adapting to new developments as necessary.

The Campbell 229-L matric potential sensor was chosen for use, in collaboration with the scientists from the other two networks. The final system design for each of the ARM sites consists of 16 sensors with supporting electronics. An hourly sampling and installation plan acceptable to ARM management was created, and was named SWATS (Soil Water and Temperature System). The sensors are deployed in two soil profiles of 8 sensors each, one meter apart, at depths of 5, 15, 25, 35, 60, 85, 125, and 175 cm below the surface (rock permitting). Nineteen of 22 planned installations have take place to date. Calibration techniques for the 229-L sensors were developed and implemented before sensors were field deployed. Soil samples for characterization of all sites have been taken, and samples for gravimetric measurements have been acquired at 11 sites. Other activities to date have included adjustment of the reference thermister in the electronics enclosure at each site to minimize noise in the data, various electronics troubleshooting, and initial analysis of raw data.

The SWATS systems have proven to be relatively robust so far, although there have been a few problems with components that failed shortly after delivery, while some have suffered damage from lightning and flash floods. Overall, the system design appears to be appropriate to the SGP environment.

Initial raw data analyses show that there is a clear signal associated with rain events and drying, with the expected trends and differences between depths. Soil scientists at Oklahoma State University, under a subcontract, are doing the laboratory work for the soil characterization and the gravimetric measurements. Once those results are known — two data points for each deployed system — we will know whether the 229-L- based estimates of volumetric soil water have acceptable error characteristics.

Validation of Satellite-Based Rainfall Algorithms Over the Tropical Pacific

An overall objective of this research is to enhance the observing capabilities of satellite-based rainfall algorithms for the Global Precipitation Climatology Project (GPCP) through validation. Specifically, the sampling characteristics of existing satellite and surface raingauge systems are being investigated, and useful volume rainfall estimates from selected Pacific raingauge networks are being constructed. To date, several high-resolution weather-monitoring stations have been established on three different islands in the Pacific Ocean. Equipment includes standard tipping bucket raingauges, a gauge-height anemometer and wind vane, and professional-quality temperature and relative humidity sensors. Eight papers have been published in the refereed literature addressing technique development and algorithm verification over the open ocean.

Plans – FY 97

Parameterization of Microphysical and Radiative Processes in Stratiform Clouds for Use in Meso and Large Scale Models

LES model simulations and observational data analyses will be used for development of the parameterization of the rain process in mesoscale models. The goal is to improve the treatment of the precipitation process by studying the details of the drop size distribution evolution and their dependence on meteorological conditions. We will conduct high-resolution experiments with the CIMMS LES model that include explicit formulation of both liquid and ice phase microphysics. The clear understanding of the physics of rain formation will be crucial for determining the minimum set of meteorological parameters needed for accurate parameterization of rain in mesoscale models.

Anthropogenic aerosols can significantly change cloud radiative properties, as vividly demonstrated by the ship track phenomena. We will continue the study of the aerosol indirect effects and will aim toward developing the parameterization of the aerosols in mesoscale models. The study will be based on the CIMMS model of stratocumulus cloud layers that explicitly formulates the effects of aerosols and cloud drop spectra.

Effects of Lightning on Global NOX

Work may begin on use of numerical cloud models that include electrification processes to investigate lightning generated NOX, to estimate the relative contribution from thunderstorms for application to the global NOX budget of the upper tropospheric and lower stratosphere.

Validation of Satellite-Based Rainfall Algorithms Over the Tropical Pacific

Future work includes participation in the 3rd Precipitation Intercomparison Project, which aims to generate areal averaged rainfall estimates over the Pacific Ocean. The signal-to-noise ratio will be utilized as a criterion for incorporation into this data set. Several solar-powered weather stations will be designed for setup on the Woleai atoll in the Micronesia. This will be a feasibility exercise to determine if an atoll makes an adequate platform for open ocean rainfall measurements. Finally, maintenance and quality control of the Comprehensive Pacific Rainfall Data Base (CPRDB) through EVAC will be pursued.

Diagnostics of Climate Variations in the Extratropical North Atlantic Sector

This research thrust will focus on the patterns, causes, and consequences of variations in the North Atlantic Oscillation (NAO), particularly as they characterize the hitherto relatively neglected eastern half of the ocean basin. This work would analyze long-term marine, continental, and satellite data to investigate alternative methods of statistically characterizing the NAO, the variability of the season-to-season progression of this mass oscillation, its relation to the weather systems and rainfall patterns over the eastern North Atlantic and adjacent continental margin (especially the sensitive 30° -50° N zone, which includes Morocco), and the NAO’s air-sea interaction involvement on time-scales ranging from interannual to multidecadal. Investigation of the roles of the above NAO variations within the Atlantic climate system will also involve analyses of the results of both previous and new dedicated GCM experiments.

Diagnosis of West African Monsoon Variability

This work will focus on the 1951-90 downtrend of monsoon rainfall in the West African Sahel, including some aspects of the interannual variability within that multidecadal trend. The variability of the distinctive West African tropospheric structure (low-level southwesterly monsoon flow, mid-tropospheric easterly wind maximum, upper tropospheric Tropical Easterly Jet) that supports the rain-producing monsoon disturbances will be investigated for the 1951-90 period using unique sets of individual rawinsonde observations, and for other decadal-scale periods using the results of GCM simulations that have already been performed (e.g., Atmospheric Modeling Intercomparison Project runs for 1979-88; decadal 1 x CO2 control runs). These findings will be related to the resulting smaller-scale monsoon disturbance characteristics (as revealed by daily rainfall data for 1951-90), the underlying larger-scale African-Atlantic basin atmospheric-oceanic-land surface conditions (e.g., meridional SST and tropospheric temperature gradients; tropical and extratropical Atlantic atmospheric circulation patterns, including the North Atlantic Oscillation, NAO; African rainfall anomaly patterns; Sahelian vegetation status) and the more global state of the climate system (e.g., tropical Atlantic versus tropical Pacific SST anomaly patterns).

Diagnostic and Predictability Studies of Precipitation Variations in Central and Eastern North America

This ongoing research program will continue to focus on three major goals — the documentation of all aspects of the intraseasonal and interannual variability of the precipitation through the advanced statistical analysis of a fine resolution set of daily precipitation data for 1949-present; the quantification of the relative importance for precipitation amount of a range of tropospheric processes that occur over the study region, especially during growing season months; and the relation of the distribution, timing, and amount of precipitation to larger climate system controls, such as tropical Pacific sea surface temperature anomaly patterns. During the coming year, this effort will begin to “nest” a weather-system-resolving regional model within a global climate model, in an attempt to obtain maximum physical insight into the crucial links in the teleconnection chain.

Large Scale Atmospheric/Oceanic Variability

Research is planned in two areas:

Catalogue of Eigenvector Patterns for Leading GCMs

A catalog of eigenvector patterns for observed geopotential heights, OLR, winds and moisture from NMC reanalysis data and other sources will be created. A complementary set of such patterns from the IMGA GCM (Italy) version of the ECHAM GCM will be derived and matched to the observed set through Procrustes Target Analysis. Such sets of patterns will fill a need for field data identified in the latest IPCC Scientific Assessment. These will be made available to the scientific research community through NCAR ftp and web sites.

Investigations of Climate Variations and Trends Associated with Tropical Variability

Two goals will be addressed concerning recent trends in tropical and subtropical height and moisture fields. The first will investigate the upward trend in geopotential height in the upper troposphere around the tropics since the 1970’s. The research will attempt to pin down the physical mechanisms on how it is related to trends in the tropical sea surface temperatures and any global warming. The role of deep tropical convection and the release of latent heat will be quantitatively documented. A Ph.D. thesis will be dedicated to this issue as well as how well current climate models capture it. The second goal aims to study the inter-relationships between the aforementioned geopotential mode and a second mode of boreal summer precipitation. These seem to both have a relationship to El Nino/Southern Oscillation, but at different lag times. This should shed light on the climate variability during the period of 1970-present.

Mesoscale Variability of Surface Fluxes and Their Large-Scale Representation

A recently developed variational data assimilation scheme will be applied to Oklahoma Mesonetwork data to estimate surface fluxes of heat, moisture, and momentum, together with effective surface roughness and skin temperature. The estimated fields will resolve mesoscale variabilities (in time and space) and will be used to improve the surface subroutine in a mesoscale model and to study parameterization of surface processes in climate models.

Atmospheric Radiation Measurement (ARM) Program Research

Work may be initiated to investigate the effects of vegetation, soil moisture, and other land surface characteristics on boundary layer conditions and on the formation of cumulus clouds over the ARM Southern Great Plains site using measurements from both the ARM network and the Oklahoma Mesonetwork.

Work may begin on use of satellite products to develop mean upper tropospheric water vapor data on regional scales for different synoptic patterns and convective frequencies/intensities. Use would be made of radiation measurements from the ARM Southern Great Plains site to assess variations in the impact of upper tropospheric water vapor and cirrus outflow on the radiation budget, and to evaluate the modeling of moisture transport by deep convective clouds in the upper troposphere.

Work may also start on use of WSR-88D data in combination with ARM data from rawinsondes, surface meteorological instruments, and profilers that obtain winds, moisture, and temperature, to obtain accurate estimates of planetary boundary layer circulations and surface fluxes for general circulation model studies.

ARM/GCIP Measurements of Soil Moisture and Temperature Profiles at the ARM Southern Great Plains Site

Tasks to be done during the coming seven months include: completing the last three instrument installations as soon as site infrastructures are built; packaging the results of the soils characterization work for use by the research community; finishing gathering the gravimetric measurements; making comparisons for each site between the 229-L estimates and the gravimetric measurements; developing, testing, and implementing automated data quality analysis algorithms; completing the evaluation of the field performance of the systems; making adjustments needed to maximize data quality and continuity; transferring documentation on instrument system hardware and software, and both preventative and corrective maintenance to SGP Site Operations; and, if data appear to be reasonable, releasing the data stream to the ARM and GCIP communities as “beta” level data.

Annual and Interannual Precipitation Variability Over the Tropical and Subtropical Americas and Eastern Pacific as Inferred from GOES Observations

Work will be funded to use high spatial resolution GOES infrared satellite imagery to validate different rainfall estimation algorithms for the region of the tropical Americas during the warm season and to use these estimates (and estimates of the original cloudiness frequencies) to describe basic characteristics of the cloudiness and rainfall variability of the region. The diurnal variation of cloudiness/rainfall, the seasonal evolution of cloudiness/rainfall, and the intraseasonal variations of cloudiness will be described at spatial resolutions higher than previously obtained. The evolution of regional features, such as the Mexican monsoon, will be an object of particular study. The cloudiness patterns will be related to atmospheric circulation patterns based on analysis of the rawinsonde data over the region.

Strengthening the Meteorological Sounding Network Over the Eastern Pacific Ocean and the Intertropical Americas to Support PACS

Work may begin to establish a radiosonde station on Cocos Island in the far eastern Pacific Ocean, located at 5.5 N, 87 W, and to establish for a similar duration several other pilot balloon stations in Central America and northern South America. These, together with a somewhat denser network to be operated for a shorter duration, will be used to evaluate the uncertainty present in the current operational analyses over this region and the representativeness of the current radiosonde sounding sites for describing lower-tropospheric variability over the region. The Cocos Island observations will also be used to help describe the annual cycle of the Intertropical Convergence Zone (ITCZ) over the region, in an area more isolated from local land-sea effects, than other sounding sites in the region.

Mesoscale Model Simulations of Interannual and Intraseasonal Variability of the Mexican Monsoon

Work may begin this FY (or in 1998) on investigation of the feasibility of accurately simulating a strongly contrasting Mexican monsoon season using the Penn State University/NCAR Mesoscale Model, leading to examination of the physical connections between rainfall over the southwest and central U.S. and help to understand El Niño linkages to precipitation over North America during summer.

SOCIOECONOMIC EFFECTS OF MESOSCALE WEATHER SYSTEMS AND REGIONAL-SCALE CLIMATE VARIATIONS

Progress – FY 96

Utilizing a Farm-Level Decision Model to Help Prioritize Future Climate Prediction Research Needs

A whole-farm level decision model was used to examine the impact of the type of decisions producers make on the value of seasonal climate forecasts for east central Texas. Results suggested precipitation forecasts directed toward crop mix and applied nitrogen level decisions would have the largest economic value. Further, the results showed that the economic value of climate forecasts couldn’t be obtained by examining only a small set of decision types. Rather, all decision types must be modeled to correctly value seasonal precipitation forecasts. This occurs because, in response to seasonal climate forecasts, changes in one type of decision may override the need to change other decision types. Finally, forecasts of precipitation during the crop tasseling and grain filling stages may be more valuable than precipitation forecasts for earlier crop growth periods.

Improved Southern Oscillation-Based Climate Prediction Information: Potential Implications at the Aggregate Level

Economic decision models incorporating biophysical simulation models were used to examine the impact of the use of Southern Oscillation (SO) information on sorghum production in Texas. Production for 18 sites was aggregated to examine the impact of the use of SO information on the aggregate supply curve and other economic variables. Two information scenarios were examined. The first scenario assumed producers do not use SO information in making their production decisions. This scenario was contrasted to a scenario in which producers use information concerning the SO in making their production decisions. For all expected prices, the use of SO information increased producers’ net returns. The expected Texas aggregate sorghum supply curve using SO information shifted both left and right of the “without information” supply curve depending on the price. Changes in nitrogen use based on the SO information were a major factor causing the shift in the supply curves. Further, the use of SO information decreased aggregate expected costs of production. Changes associated with the use of SO information can be summarized as follows — the use of SO information provides producers a method to use inputs more efficiently. This more efficient use has implications for both the environment and for the agricultural sector.

Using the Southern Oscillation to Forecast Crop Yields

Time series models were used to examine the impact of Southern Oscillation (SO) extreme events in estimating and forecasting Texas sorghum and winter wheat yields. Results were both crop and period specific. Including SO events in forecasting yields decreases the forecast mean square error for winter wheat but had no significant impact on sorghum forecasts. Further, it was shown that a significant correlation between SO events and yields does not necessarily translate into better yield forecasts.

Plans – FY 97

Modern Meteorology and the Insurance Industry: Meteorological Capabilities and Uncertainties and Insurance Industry Needs

During the next year, we propose to significantly enhance a carefully structured dialogue between the meteorological and the insurance communities that we are undertaking in partnership with the Insurance Institute for Property Loss Reduction (IIPLR). This dialogue will focus on how the capabilities of modern meteorology can be used to reduce the toll on life and property resulting from severe weather and climate change, and enhance the competitive positions of proactive primary insurance companies. It will explore how the insurance industry can better use weather and climate information in strategic planning, in anticipating and mitigating losses of insured property, and in operational decisions responding to weather-related catastrophes.

An Investigation of the Occurrence of Freezing Temperatures in the Southeastern United States and Their Relationship with Insurance Claims and Losses due to Pipe Bursting

The investigation of this topic will be pursued through both individual and combined analyses of temperature and insurance claim data sets. It will exploit a fine resolution set of daily maximum and minimum temperature values for 1950-92, along with insurance claim data for the 1986-92 period that includes several catastrophic freezing events. A principal goal is to identify spatially varying key minimum temperature thresholds that are associated with a similar region-wide claim rate. The relations of these parameters to the economic values of the claims will also be investigated. The project is intended to offer guidance for the formulation of building code policy by the property insurance industry.

Effects of Seasonal Climate Forecasts on Competitiveness in the Grain Market

The long-term competitiveness of United States agriculture centers on its adoption of technological advances. Recent developments in the science of meteorology are providing the means to more accurately predict seasonal climatic conditions. (Climate refers to the weather conditions associated with time periods of approximately 2 weeks or longer.) Improved forecasts will alter producers’ selection of inputs and expectations of output price. Such changes would affect cropping patterns and the use of production inputs that subsequently alter regional and national supply curves. These changes will impact the competitiveness of the United States in international markets. Currently, Australia has improved seasonal climate forecasts that are being made available to the private sector decision-makers. To our knowledge, no study has focused on how these improved climate forecasts affect international competitiveness. The main objective of this proposed study is to address this void by evaluating the role of enhanced climate forecasting ability on international competitiveness in the world grain market. This work is being performed in collaboration with agricultural economists at Texas A & M University.

DOPPLER WEATHER RADAR RESEARCH AND DEVELOPMENT

Progress – FY 96

NSSL/OSF WSR-88D “Re-Host” Effort

NSSL was tasked by the NWS to perform the software development for “re-hosting” the WSR-88D Radar Product Generator (RPG) to an open systems environment. The NWS and ERL signed a Memorandum of Understanding in August 1995 for undertaking this task. Work began shortly thereafter, which included gaining an understanding of the current RPG, initiating the design and development of the Open Systems RPG (ORPG) software infrastructure, determining the best techniques and developing the support software to port the legacy RPG algorithms and product generators to the ORPG environment, and the development of a new Graphical User Interface (GUI) Unit Control Position (UCP).

Plans – FY 97

NSSL/OSF Radar Research and Development (including Re-Host)

The NEXRAD Program (NWS/ Federal Aviation Administration – FAA/Department of Defense – DOD) has a requirement to evolve the WSR-88D system by taking advantage of new science and state-of-the-art computer hardware in order to enhance the performance of the radar and improve weather warning capabilities. The first major effort in system evolution will be the “re-host” of the Radar Product Generator (RPG) software to new open system computers and modern communications technology, using modern open system standards, interfaces, compilers, and software design techniques. The new open system RPG will allow for more rapid introduction of new science into the system. The second major effort in system evolution will be the re-host of the Radar Data Acquisition (RDA) software to new open system computers. As part of this effort, new signal processors will be incorporated that, along with the open system computers and software, will allow new data acquisition, clutter suppression, and anomalous propagation techniques to be incorporated into the systems. One of the major enhancements that may be added to the system to take advantage of the evolved radar design is dual polarization. These system evolution activities are being undertaken by NWS using the staffs of the OSF, NWS headquarters, and NSSL, and will be augmented by OU personnel.

Specific re-host functions will include the establishment of a functioning ORPG thread that includes the ported algorithms operating on either real-time radar data or archived radar data, full software infrastructure support, product request and distribution services, RDA control and monitoring, and further development of the GUI UCP.