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Relationship between Antecedent Land Surface Conditions and Precipitation in the North American Monsoon Region
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Chunmei Zhu , Dennis P. Lettenmaier , and Tereza Cavazos
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Department of Civil & Environmental Engineering, Box 352700, University of Washington, Seattle, WA 98195
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Department of Physical Oceanography, Centro de Investigacion Cientifica de Educacion, Superior de Ensenada, Ensenada, Mexico
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Winter Precipitation - JJAS Monsoon West Rainfall
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Introduction
Higher or lower winter precipitation
& winter , spring snow
We explore possible links between North American Monsoon System (NAMS) seasonal (Jun-Jul-AugSep) precipitation and pre-monsoon (previous autumn, winter, and spring) land surface conditions,
including precipitation, temperature, soil moisture and snow cover anomalies. We hypothesize land and
sea surface feedback mechanisms associated with NAMS precipitation, and we propose an approach
for determining their dynamical links. Following previous investigators, we partitioned the NAMS
region into four sub-regions (Monsoon West, South, North and East) based on the seasonality and
variability of JJAS monsoon precipitation from 1961-1990, and evaluated the possible effects of
previous land surface conditions in various subcontinental “predictor regions” on Monsoon West (MW)
monsoon precipitation. Data for the study were monthly aggregates from the retrospective Land Data
Assimilation System (LDAS) archive for the period 1950 to 1999. The retrospective LDAS archive
includes gridded precipitation (P), mean surface air temperature (Ts), and Variable Infiltration Capacity
(VIC) land surface model-derived soil moisture (Sm), and snow water equivalent (SWE). We outline
future work that will construct an exploratory seasonal monsoon precipitation predictive model based
on antecedent conditions.
References:
Comrie A.C. and E.C. Glenn, 1998: Principal components-based regionalization of precipitation regimes across the southwest United
States and northern Mexico, with an application to monsoon precipitation variability. Clim. Res., 10, 201-215.
Higgins R.W. and W.Shi , 2000: Dominant factors responsible for interannual variability of the summer monsoon in the Southwestern
United States. J. Climate, 13, 759-776.
Hu Q. and F. Song, 2002: Interannual rainfall variations in the North American Summer Monsoon Region: 1900-98. J. Climate, 15, 11891202.
Liang, X., D. P. Lettenmaier, E. F. Wood, and S. J. Burges, 1994: A Simple hydrologically Based Model of Land Surface Water and
Energy Fluxes for GSMs, J. Geophys. Res., 99(D7), 14,415-14,428.
Lo F. and M.P. Clark, 2002: Relationships between spring snow mass and summer precipitation in the Southwestern United States
associated with North American monsoon system. J. Climate, 15, 1378-1385.
Matsui T, V. Lakshml and B. Small, 2003: Links between snow cover, surface skin temperature, and rainfall variability in the North
American Monsoon system. J. Climate, 16, 1821-1829.
Maurer E.P., A.W. Wood, J.C. Adam, D.P. Lettenmaier, and B. Nijssen, 2002: A long-term hydrologically-based data set of land surface
fluxes and states for the conterminous United States. J. Climate, Vol. 15, 3237–3251.
Guzler D.S., 2000: Co variability of spring snowpack and summer rainfall across the southwest United States. J. Climate, 13, 4018-1027.
Gutzler D.S. and J.W. Preston, 1997: Evidence for a relationship between spring snow cover in North America and summer precipitation
in New Mexico. Geophys. Res. Lett., 24, 2207-2210.
Winter Precipitation-monsoon rainfall feedback hypothesis
More or less spring or
early summer soil moisture
lower or higher spring and early
summer surface temperature
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Figure 2a: Monsoon West winter predictor region.
Weak or strong monsoon
Winter precipitation – spring soil moisture link
Figure 2b: 15-year moving correlation of
JJAS rainfall versus related winter
precipitation predictor indices
● The statistically significant negatively related region includes southern California,
Nevada, Utah, Arizona, western Colorado and New Mexico, which is potential winter
predictor region for Monsoon West monsoon rainfall (figure 2a).
● This negative relationship is not robust always. It is strong during the 1965-1990
period, but weak in other periods from 1950-1999.
The land has a memory effect from winter precipitation anomaly. During extreme years,
the soil moisture anomaly signal persists through April. May and June. Great Plain and
Southwest show reverse signal.
●This negative signal is very strong during extreme years (Figure 2c).
Soil moisture – surface temperature link
April soil moisture has a negative , but
not very strong correlation with May ,
Figure 3c: Monsoon West
JFM relative precipitation
anomaly composite for wet and
dry years. Period: 1965-1999.
June surface temperature.
Snow – surface temperature link
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Study Domain
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Snow-monsoon Relationship
April snow index shows a strong negative
correlation with May & June surface
temperature in the Four Corners region.
Pre-monsoon surface temperature – monsoon
Antecedent June Ts in Northern AZ and in the Southern
Rockies is positively correlated with July monsoon West
rainfall. It seems that in the core of the monsoon the
relationship is negative, possibly because rainfall there
comes earlier…The land –surface mechanisms associated
with surface temperature and rainfall needs further
investigation
Monsoon East
Monsoon South
Monsoon North
Conclusions:
Monsoon East
Figure 3a: Monsoon West snow index area
Monsoon regions are defined as Comrie & Glenn paper (Climate Research, 1998, Vol10
: 201-215) based on the seasonality and variability of JJAS monsoon precipitation from 19611990, and in the following section we evaluated the possible effects of previous land surface
conditions in various subcontinental “predictor regions” on Monsoon West (MW) monsoon
precipitation.
Figure 3b: 15-year moving average correlation of
Monsoon West snow index versus JJAS monsoon
rainfall
● For North American Monsoon region (here referring to western AZ and eastern NM),
Four Corners region show a strong negative correlation with monsoon rainfall.
land surface-monsoon relationships are not stable in time. 1965-1990 is the significant
period over 1950-1999. Southwest US winter precipitation, Four Corners regions and
mountainous area of Nevada and Utah spring snow have negative correlation with JJAS
monsoon.
● This negative relationship is strong during 1965 – end of 1980s.
● Antecedent land surface link that we propose (SWE, Sm, and Ts) is stronger in the Utah
● JFM & April SWE in the mountainous portions of Utah and Nevada and the
and Nevada mountain and Four Corners source areas where SWE may play a significant
role in underpinning the land surface memory effect into the atmosphere. However the
surface temperature – monsoon link need further investigation