Observing and Understanding the Variability of Water in Weather and Climate


Regional Data Assimilation at NCEP: Recent advancements in the assimilation of precipitation, clouds, water vapor, soil moisture and snowpack (Invited Presentation)

Kenneth E. Mitchell, NOAA/NWS/NCEP, Camp Springs, MD; and E. Rogers, D. Parrish, Y. Lin, G. DiMego, M. Ek, D. Lohmann, B. Ferrier, F. Mesinger, P. Shafran, and W. Wu

This presentation reviews the recent history, present status, and future plans of the Eta-model based regional 4-D data assimilation system (EDAS) at NCEP, with a focus on the water cycle components of precipitation, clouds, water vapor, soil moisture, and snowpack. Additionally, we present the objectives, configuration and status of NCEP's emerging 25-year Regional Reanalysis, based on re-executing the July 2001 operational version of the EDAS over the 25-year period of 1979-2004. Several of the major milestones in the ongoing life-cycle of EDAS development at NCEP included a) replacement of optimum interpolation analysis (OI) with the 3-D variational analysis (3D-VAR) on 09 Feb 98, b) introduction of fully continuous EDAS cycling (eight 3-hour cycles per day), including full cycling of cloud condensate and the land/soil states, on 03 Jun 98, and c) assimilation of hourly 4-km radar/gage precipitation analyses on 24 Jul 01. In addition to the assimilation of precipitation, other water-related variables assimilated in the EDAS are 1) - water vapor profiles from rawinsondes and dropwinsondes, 2) - surface dew point observations from land stations, ships, and buoys, 4) GOES precipitable water over land and SSM/I precipitable water over ocean, and 5) GOES moisture channel radiances over ocean. The resolution of the EDAS (and Eta forecast model) has increased from 48-km/38-layer on 12 Oct 95, to 32-km/45-layer on 9 Feb 98, and then to 22-km/50-layer on 26 Sep 00, and finally to the present operational resolution of 12-km/60-layer on 27 Nov 01. Our examples of the impact of the above upgrades will focus on the precipitation assimilation and the continuous cycling of land states such as soil moisture, including examples of season to season and interannual variations of EDAS soil moisture over such areas as the southwest U.S. monsoon region. We will show how external researchers have employed archives of EDAS output maintained since April 1995 to conduct multi-year studies of the hydrological cycle over the Mississippi River basin and elsewhere. Additionally, we will show results from present NCEP experiments to 1) assimilate GOES cloud information and 2) fully cycle all four species of cloud condensate in the EDAS cloud microphysics. Additionally, we will present examples from pilot runs of the 32-km/45-layer EDAS-based Regional Reanalysis and highlight the notable improvements of its precipitation patterns over that of the previous NCEP/NCAR Global Reanalysis. Finally, we will introduce pilot results from the new NCEP Land Data Assimilation System (N-LDAS) and show plans for the EDAS-like 3D-VAR assimilation system for the new nonhydrostatic Weather Research and Forecast Model (WRF).

Session 5, Assimilation of water data in all its phases
Thursday, 13 February 2003, 1:30 PM-4:30 PM

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