NOAA’s Climate Prediction Center &

*Environmental Modeling Center

Camp Springs, MD 20746

Impact of High-Frequency Variability of Soil Moisture on Seasonal Precipitation

Song Yang, S.-H. Yoo

R. Yang*, K. Mitchell*, H. van den Dool, and R. W. Higgins

Table of Contents

Motivation

Model and experiments

Results, explanations, & summary

Future work

Yang and Lau (1998; J. Climate)

Motivation

NCEP Eta Regional Climate Model

Resolution: 32-km in horizontal; 45 levels in verticalDomain: 10N-90N, 164W-58W

Noah Land Model 2.3, with 4 soil layersImplemented in Operational NCEP Eta ModelImplemented in NCEP Regional Reanalysis

Boundary conditions: NCEP/NCAR Global Reanalysis Initial conditions: NCEP/NCAR Global Reanalysis U.S. Air Force daily analysis of snow depthInitial land states: NCEP Regional Reanalysis

Model

Period: May-August of 1988 and 1993Starting months: AprilLength of integrations: 4 monthsNumber of ensemble members: 5SST, surface albedo, and greenness: Updated daily

Data of verifications: NCEP Regional Reanalysis; NCEP Land Data Assimilation System; CPC Unified Precipitation; and Global Telecommunications

Experiments

Soil moisture as surface boundary forcing in sensitivity experiments:3-hourly meansDaily meansWeekly means

Results I: Control Runs

Model-observation comparison

Precipitation (1993-1988)

Eta

RR CPC

Surface Temperature (1993-1988)

Eta

RR GTS

Soil Moisture (1993-1988)

LDAS data from Dr. Yun Fan

Results II: Sensitivity Experiments

Soil moisture as surface boundary forcing:3-hourly means

Daily meansWeekly means

Roles of diurnal cycle & sub-synoptic variability of soil moisture

JJA 1988Precip

3 Hourly

3H-Daily

3H-Weekly

Ts

TsJJA 1988T850

3 Hourly

3H-Daily

3H-Weekly

850-mb Winds

JJA 1988

3H-Weekly

3H-Daily

3 Hourly

Precip of JJA 1988 Precip of JJA 1993

3 Hourly

3H-Daily

3H-Weekly

3H-Weekly

Ts of JJA 1988 Ts of JJA 1993

3 Hourly

3H-Daily

3H-Weekly

T850 of JJA 1988 T850 of JJA 1993

3 Hourly

3H-Daily

3H-Weekly

JJA 1988

JJA 1993

3 Hourly

3H-Daily

3H-Weekly

Explanations

• Reasonable performance by Eta

• Impact of sub-synoptic soil moisture variability

• HF var. of soil moisture changes seasonal means of precip.

• Different roles between 1988 and 1993

• Importance of diurnal cycle

• Dynamical consistence

• Explanation (water and heat fluxes, instability, etc.)

Summary

Future Work

Impact of the spatial structure of soil moisture