The tenth IMSC, Beijing, China, 2007 - International Meetings on ...

<strong>The</strong> magnitude of the change signals both in mean and extremes of temperature and
precipitation in response to anthropogenic forcings is more pronounced in 2051-2080
compared to the period of 2021-2050 as GHG concentration increased. <strong>The</strong> temperature
exhibits a positively persistent trend throughout whole period increasing by 3.2°C for 2070s
while precipitation is characterized by pronounced interdecadal variations, with gradual
amplification of the fluctuation range. During wet period, the summer monsoon is intensified
due to stronger southeasterly flow, favorable for advection of lower level warm and moist air
from the Pacific Ocean. A significant increase (decrease) of hot (frost) spells is found along
with increasing (decreasing) of maximum (minimum) temperature. <strong>The</strong> frequency distribution
of daily precipitation during 2051-2080 indicates heavy rainfall over 400 mm/day, suggesting
the possibility of increasing frequency of flood events. Wet spells of long periods tend to be
more frequent as well, accompanied with an increase of precipitation amounts
Trend Indicators of Atmospheric Climate Change based on Reanalyses and Global Climate
Model Scenarios
Bettina C. Lackner
bettina.lackner@uni-graz.at
Andrea K. Steiner
Florian Ladstaedter
Gottfried Kirchengast
Wegener Center for Climate and Global Change (WegCenter), University of Graz, and Institute for
Geophysics, Astrophysics, and Meteorology (IGAM), University of Graz, Austria
<strong>The</strong> upper troposphere-lower stratosphere (UTLS) region is re-acting particularly
sensitive to climate change. Thus, changes of the thermodynamic state of this part of the
atmosphere, especially variations of its key parameters, are promising candidates for the
monitoring and diagnosis of climate change.
This study aims at revealing optimal atmospheric climate change indicators with respect
to radio occultation (RO) measurements, which feature high accuracy, long-term stability, and
global coverage. As a first step, due to the currently limited time length of RO observations, we
investigate ‘proxy’ climatologies from reanalyses and global climate model runs. We use two
reanalysis data sets and three representative climate models with two representative
scenarios for the IPCC 4th Assessment Report serving as multi-decadal datasets out to year
2050. <strong>The</strong> datasets are systematically explored for finding the most robust and sensitive trend
indicators by testing pre-defined potentially useful atmospheric parameters such as refractivity,
geopotential height, temperature, and specific humidity. <strong>The</strong>se key climate variables were
chosen since they are provided by RO measurements with highest accuracy.
Temporal characteristics of trends are analyzed on the basis of a seasonal resolution. Different
investigated spatial domains (e.g., northern/southern hemisphere, tropics, mid-latitudes, as
well as UT, LS) allow a mapping of regions, which are particularly suitable for trend indicators.
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