Water Vapor - IHOP (see Accomplishments Section) focused on improving the ability to forecast convective rainfall amounts by deploying and evaluating an unprecedented suite of water vapor sensors. The IHOP PI's concentrated on designing aircraft tracks for multiple aircraft missions; coordinating various investigator's activities; organizing and running planning meetings; serving on the P-3 transition team to ensure the first-ever P-3 deployment of ELDORA and the French Leandre II water vapor DIAL; and overseeing logistical planning for field operations. The yearlong planning effort culminated in a 2-month-long intensive field campaign. Over 200 researchers coordinated activities and obtained measurements on convection initiation events, low-level jets, bores, clear-air boundary layers and heavy rainfall events. Initial analysis of data and reports from investigators indicate that this project was a complete success.

To the left is one of the most complicated flight tracks that was flown during IHOP, involving all six research aircraft

Water Vapor - Microwave Profiling Radiometer (MWRP) - This is a study of the diurnal variations of temperature and water vapor profiles using data from a new microwave profiling radiometer (MWRP) deployed at the ARM-CART site near Lamont, Oklahoma. MWRP temperature and humidity data and their diurnal variations were compared with radiosonde data. Other data were analyzed to understand observed diurnal variations.

Radiosonde Humidity Data - Coincident soundings were compared and measured by Vaisala RS80 and VIZ B2 radiosondes during the TRMM LBA in 1999. The comparison shows significant differences between Vaisala and VIZ humidity data, which cannot be explained by known problems associated with these two radiosonde types. Indirect comparisons of Vaisala and VIZ data from TOGA_COARE and the TRMM Kwajex experiment also showed these same features. This research led to development and deployment of a reference radiosonde capable of carrying both the Vaisala and VIZ humidity sensors. These flights were made during IHOP-2002.

The left panel shows mean relative humidity (RH) profiles from Snow White (SW, reference humidity sensor), the carbon hygristor inside the reference sonde (RS) and Vaisala RS80-H. The comparison of SW and Vaisala shows that Vaisala RS80-H has very good performance in the lower and middle troposphere, but has a dry bias in the upper troposphere. The right panel shos mean RH profiles from SW, the carbon hgristor inside RS and carbon hygristor inside NWS VIZ radiosonde. It shows that the carbon hygristor fails to respond to humidity changes in the upper tropsophere (no sensitivity at all) and the hygristor inside RS has slower response than that inside NSW VIZ radiosonde although the two hygristors are exactly the same.

Sydney 2000 Forecast Demonstration Project - Analysis of data from this experiment is nearing completion. A special issue of Weather and Forecasting is being prepared which describes the results from this experiment. This analysis showed the NCAR thunderstorm nowcasting system called the Auto-nowcaster was the only system capable of providing statistically better nowcasts than extrapolation.

Boundary Layer Turbulence and Fluxes - In collaboration with scientists from NCAR/MMM, Johns Hopkins University, and Pennsylvania State University ATD researchers used data collected in September 2000 during the HATS (Horizontal Array Turbulence Study) field project to investigate the statistical properties of turbulence partitioned into spatially-resolved and sub-filter-scale (SFS) components, as assumed in Large Eddy Simulation (LES) models. Work over the past year has focused both on quantifying the accuracy of computational algorithms used to estimate spatially-filtered statistics and the spatial gradients of those statistics and on examining the properties of SFS turbulence.

Surface Energy Budgets - ATD researchers participated in analysis of Energy Balance Experiment (EBEX-2000) data to determine why closure of the energy balance utilizing basic physical measurements, such as sensible and latent heat flux, net radiation, soil heat flux and storage, is difficult. Typically the error is larger than expected from an error analysis of the individual terms.

Tropical Convection - Recently published work shows that tropical convection has a strong sensitivity to middle level relative humidity. This result, suggested by earlier measurements taken during TOGA COARE, was confirmed using cloud resolving model simulations. ATD researchers collaborated with investigators from the Japanese Marine Science and Technology Center (JAMSTEC) on a study showing the diurnal variation of tropical deep convection was likely due to diurnal variations in stability, not to cloud-radiative interactions.

Hurricane/Tornado - ATD researchers refined the objective vortex circulation center finding algorithm and the VTD/simplex algorithm. A more sophisticate weighting system that takes into account the time continuity of radius of maximum wind, position of the vortex center, and the maximum mean tangential wind can reduce the uncertainty in the objectively determined vortex centers using the maximum mean tangential wind as the sole criteria and thereby improve retrieved vortex circulations. The Mulhall tornado data were reanalyzed using these new vortex centers. The overall structures of the tornado improved significantly.

NEXRAD Data Quality Optimization Program - The AP clutter mitigation scheme was deployed on S-POL for the IMPROVE-II and the IHOP field experiments. The radar echo classifier algorithms and the reflectivity-velocity compensation algorithms were run during field operations. Ongoing research is with the radar echo classifier (REC), a fuzzy logic algorithm that estimates the type of echo present in each gate (precipitation, ground clutter or insect clear air return). This year a set of confidence algorithms for each of the REC algorithms was developed and tested in the field during IMPROVE-II and IHOP.