Short-term Prediction Research
and Transition Center

Modeling & Data Assimilation Projects

Towards Improved Modeling of Land-Atmosphere Interactions using NASA Systems and Tools

Motivated by the positive results found using MODIS data to initialize sea-surface temperatures (SSTs) in numerical weather prediction (NWP) models [LaCasse et al. (2007)], this project attempts to improve the specification of the lower boundary in regional NWP models over land areas. The NASA Goddard Space Flight Center Land Information System (LIS) software is being configured to optimize land and soil-state variables for initializing high-resolution regional simulations of the Weather Research and Forecasting (WRF) model for a case study period from May 2004.

The hypothesis for this project asks whether short-term mesoscale numerical forecasts of sensible weather elements can be improved by using optimally-tuned, high-resolution land surface and soil fields. Therefore, the primary goal is to investigate and evaluate the potential benefits of high-resolution land surface and soil data derived from NASA systems and tools on regional short-term numerical guidance (0-24 hours). Using the Goddard Space Flight Center LIS software coupled to the Advanced Research WRF model for improving land/soil states, SPoRT is examining a one-month period of relatively benign weather to quantify possible increased skill of WRF numerical simulations due to optimized land/soil properties.

The benefits of using LIS and coupling the system to WRF are several-fold. First, the soil initialization fields provided by LIS are at a resolution consistent with that of the regional WRF grid. Second, using LIS allows the user to optimize the surface and soil initialization variables. In addition, users have the ability to run additional land surface models (LSMs) within LIS that are not available in the standard WRF model. Finally, the LIS software provides a framework for incorporating unique NASA-derived land datasets.

The methodology involves running the Noah LSM within LIS in an offline mode (i.e. not coupled to WRF) to provide land/soil initialization data on the WRF grid. Twenty-four hour simulations of the standard WRF are then compared to coupled LIS/WRF experiments during May 2004 over Florida and southern Georgia. All simulations are run on a high-resolution domain with 3-km horizontal grid spacing. The impacts are then examined on predicted atmospheric variables, focusing on low levels. Finally, verification statistics are compiled at surface observation locations to quantify any improvements in forecast skill.

Follow-on work includes examining the impacts of the LIS/WRF system on convective initiation (in conjunction with the NSSL/SPoRT collaboration), merging the LIS capability with the MODIS-derived SSTs to improve the overall lower-boundary specification for regional modeling in coastal zones, and possibly running LIS with additional LSMs besides the Noah.

Comparison between the 0-10 cm volumetric soil moisture interpolated from the 40-km Eta model (left) and the LIS-generated field on the 3-km WRF grid (right), valid at 1200 UTC 31 May 2004. Note the high amount of detail in the LIS field, created from a 9-month LIS spin-up run on the WRF grid.

Land Information System web page:
http://lis.gsfc.nasa.gov/index.shtml

Link to SPoRT presentation at the AMS 21st Conference on Hydrology:
http://ams.confex.com/ams/87ANNUAL/techprogram/paper_116826.htm