AIRBORNE MEASUREMENT OF LAND-SURFACE ENERGY, WATER AND CARBON FLUXES OVER HETEROGENEOUS
Hydrology and Remote Sensing Laboratory
2008 Annual Report
1a.Objectives (from AD-416)
To determine spatially averaged evapotranspiration, as well as carbon and heat fluxes, between the plot and the regional scale (~20km) using a dedicated flux aircraft over irrigated agricultural region in the Texas High Plains (THS), to process and analyze the flux data using different aggregation techniques to enhance the utility of the data set for ALEXI/disALEXI model validation, scaling, and verification studies, and to provide additional flight activities and data collection to enhance the multi-disciplinary research occurrring during the intensive observation periods (i.e., providing boundary layer development data).
1b.Approach (from AD-416)
Work with UA_AERO scientist to coordinate and execute a series of airborne flux measurement campaigns. Use the resulting large-scale flux datasets to contrain/validate ALEXI model estimates and improve embedding algorithms.
The goal of this project is to implement, maintain, and improve an automated near-realtime land-surface flux modeling system (ALEXI), and to investigate the utility of resulting soil moisture proxy signatures in terms of weather forecast initialization. ALEXI surface flux estimates facilitated the retrieval of soil moisture through the development of a representative relationship between fPET (fraction of actual to potential evapotranspiration) and fAW (fraction of available water). The retrieval of ALEXI soil moisture was tested during several composite periods during the 2002-2004 time periods over the Oklahoma Mesonet. ALEXI soil moisture estimates at 10km resolution were validated against soil moisture observations from the OK Mesonet, indicating good agreement with in-situ observations. ALEXI soil moisture was also quantitatively compared to soil moisture estimates from the Eta Data Assimilation System to assess the advantages of using ALEXI soil moisture estimates within numerical weather prediction simulations. The implementation of ALEXI soil moisture during two case study periods showed positive impact with respect to daytime forecasts of 2-meter air and dewpoint temperature when compared to control simulations. The data ingestion infrastructure for the ALEXI model has been fully automated and connected with upgraded input data sources. A 10-km resolution ALEXI model grid now runs in near-realtime each evening, processing ET and moisture stress conditions over the continental US for that day. Validation of high spatial resolution (100m) soil moisture retrievals over the state of Nebraska is currently underway.
The ADODR has monitored the progress of this project through email correspondences, conference calls and periodic meetings with University of Alabama scientists.