Cooperative Institute for Research in Environmental Sciences

Changes in Arctic atmospheric moisture as shown by six reanalyses

Andrew P. Barrett, Mark C. Serreze, Julienne Stroeve

NSIDC-CIRES

We examine recent changes in tropospheric water vapor in the Arctic using output from six reanalyses. Global Climate Models indicate warming will be accompanied by increases tropospheric water vapor. These changes will likely also occur in the Arctic. The Arctic is undergoing considerable changes. In the past decade, there have been substantial increases in tropospheric air temperatures in the Arctic that are larger than those observed for the globe as a whole. This warming is largest in the cold season. September minimum sea ice extent in the Arctic Ocean has declined, with extreme minima occurring in each year since 2002. Increases in moisture transport from lower latitudes, increased temperatures and increased exposure of open water, especially in fall, are all likely to contribute to increased tropospheric water vapor in the Arctic.

Atmospheric reanalyses are used widely to study the climate system because they provide temporally complete time series of atmospheric variables with full spatial coverage at standard levels. This is a key advantage over surface and radiosonde stations which have limited spatial coverage at high latitudes. However, inconsistencies can arise in reanalyses because of changes in observing systems. Care must be taken when using renalyses to examine trends. With this caveat in mind, we examine spatial patterns and seasonal changes in Arctic tropospheric water vapor in six reanalyses; MERRA, CFSR, JRA-25, ERA-Interim, ERA-40 and NCEP/NCAR. Data from reanalyses are also compared with profiles of tropospheric water vapor from Arctic radiosonde stations. Clear differences exist between reanalyses. All reanalyses have trouble recreating near-surface profiles of water vapor observed in radiosonde.