•Pg. 1 The role of ocean and atmosphere biases on land precipitation- biases during Indian Summer Monsoon in CFS forecasts Bala Narapusetty 1,2 , Raghu Murtugudde 1 , Arun Kumar 3 , Hui Wang 3 2015-Feb18-22 1 – ESSIC, UMD 2 – Hydrological Sciences Laboratory, NASA/GSFC 3 – NOAA Climate Prediction Center
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Pg. 1 The role of ocean and atmosphere biases on land precipitation-biases during Indian Summer Monsoon in CFS forecasts Bala Narapusetty 1,2, Raghu Murtugudde.
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•Pg. 1
The role of ocean and atmosphere biases on land precipitation-biases during Indian Summer Monsoon in
• Motivation: Systematic dry-precipitation bias over
land and wet-bias over Eastern-Equatorial Indian Ocean• Analysis
• Impacts on local Hadley circulation• Biases in equatorial crossing of ITCZ in April/May• Biases in Findlater jet and Monsoon precipitation• Spatial structure of March-initialized forecast biases in
precipitation, SST and zonal wind.• Precipitation pattern correlations over the land and in
BoB
• Results and conclusions• Overall-picture: Schematic-view of bias propagation• Summary
Details of datasets used in this study
Pg. 3
• Forecast data:• CFSv2 monthly-mean forecasts (up to 11 lead-
months) obtained by initializing around the beginning of each month from 1982-January to 2011-March.
• 24 ensemble forecasts each month.
• Observations• Precipitation: APHRODITE
Gauge-based and 0.25o spatial-resolution (http://www.chikyu.ac.jp/precip)CPC and GPCP : As needed
Mass flux stream function (averaged over 60E-110E)
CFSR
CFSTG#1
CFSTG#3
CFSTG#2
The Y-axis shows pressure in hPa
The Equatorial crossing of ITCZ in the month of
Apr/May is crucial for Monsoon rainfall
(shading units in mm day-1)
Averaged over 70o-95oE
N. Eq. : Eq-5oN; 70o-95oECI : 16.5o-26.5oN; 74.5o-86.5oE
In the March-initialized April forecast, the ITCZ is mostly stuckaround Equator and results in excess precipitation during May.The land-biases grew into JJA.
Pg. 8
(shading units in mm day-1)
Averaged over 50o-70oE
Pg. 9
Averaged over 90o-110oE
The ITCZ averaged averaged 50o-70oE and 90o-110oE
Negative biases in Findlater jet grew with longer-lead