Project Details
Projekt
The Atmospheric Side of the Freshwater Budget
Applicants
Professor Dr. Stefan Bühler; Dr. Rainer Hollmann
Subject Area
Oceanography
Term
from 2013 to 2020
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 198122929
Objective: The main scientific objective of the project is to improve the understanding of the mean state and interannual variability of Atlantic precipitation areas from extratropical storm tracks to tropical rain belts. Besides this, the project has the objective to provide global data on the atmospheric side of the freshwater budget to the oceanographic groups, namely evaporation, precipitation, and atmospheric moisture convergence / divergence data. Over the open ocean, evaporation minus precipitation is the key boundary condition for ocean salinity modeling. The project will also act as general link between Research Group 1740 and the atmospheric research community. Background: Atmospheric processes related to moisture have recently been pointed out as "grand challenges" for climate research. The challenge is that they couple the large-scale atmospheric circulation to small-scale processes such as convection and precipitation. Patterns of precipitation are strongly influenced by the large-scale atmospheric circulation, but the large-scale circulation is also influenced by precipitation, and how it self-organizes in convective areas. A question that has been particularly highlighted recently is which factors control the position, strength, and variability of tropical rain belts and extratropical storm tracks, respectively. Approach: The key tasks of the project are: 1. Analyze the mean state and interannual variability of precipitation areas over the Atlantic. This includes an analysis of the correlation with dynamical phenomena on multi-annual timescales, such as the North Atlantic Oscillation (NAO) and the El Niño Southern Oscillation (ENSO). The analysis will use new data sources that have hitherto not been available, namely HOAPS4 as a global ocean satellite data set, OceanRAIN as an insitu validation data set, and the latest available GECCO2 data (from TP3.1) for the ocean state. It will also be reassessed, to what extent climate models correctly cover the mean state and variability, given the new observational data. 2. Analyze sinks, sources, and spatiotemporal variability patterns inherent to evaporation and precipitation, utilizing the calculated water vapor transports. The budget closure and consistency between precipitation/evaporation patterns and water vapor transports will be assessed. This includes an error budget assessment of moisture flux estimates, considering HOAPS uncertainty estimates and the results of the GECCO2 ocean reanalysis. 3. Contribute updated evaporation and precipitation data to the other research group members. For HOAPS this is an in kind contribution from the EUMETSAT Satellite Application Facility on Climate Monitoring, hosted by the German Meteorological Service DWD, not funded through this application. For OceanRAIN it is an in kind contribution from CliSAP / University of Hamburg, also not funded through this application.
DFG Programme
Research Units
