George C. Craig

The convective and orographically-induced precipitation study

Abstract The international field campaign called the Convective and Orographically-induced Precipitation Study (COPS) took place from June to August 2007 in southwestern Germany/eastern France. The overarching goal of COPS is to advance the quality of forecasts of orographically-induced convective precipitation by four-dimensional observations and modeling of its life cycle. COPS was endorsed as one of the Research and Development Projects of the World Weather Research Program (WWRP), and combines the efforts of institutions and scientists from eight countries. A strong collaboration between instrument principal investigators and experts on mesoscale modeling has been established within COPS. In order to study the relative importance of large-scale and small-scale forcing leading to convection initiation in low mountains, COPS is coordinated with a one-year General Observations Period in central Europe, the WWRP Forecast Demonstration Project MAP D-PHASE, and the first summertime European THORPEX Regional...

A GCM Investigation into the Nature of Baroclinic Adjustment

Abstract Spindown experiments have been conducted, using an atmospheric general circulation model, to determine the nature and timescale of adjustment to a baroclinically neutral state. The spindown was obtained by turning off the radiative cooling of the atmosphere—a procedure, the authors argue, that retains all the relevant constraints on the atmospheric motions. A further experiment with radiation and all other physical parameterizations turned off was performed for comparison. The neutral state was characterized by increased static stability but little reduction in meridional temperature gradient in the main baroclinic zones. However, the zones were observed to narrow and were flanked by regions where the meridional temperature gradient was reduced significantly. This pattern was repeated in the no-physics spin-down experiment but, in the absence of surface friction and strong orographic drag, the flow also appeared to be stabilized by enhanced barotropic shear. The neutral states from these two expe...

Sensitivity of quantitative precipitation forecast to height dependent changes in humidity

The impact of humidity variations on QPF is studied performing a series of sensitivity experiments with the COSMO model at a horizontal mesh size of 7 km. Generally, variations of humidity in the boundary layer have the largest impact on precipitation, and the sensitivity decreases with height. An increase of humidity by 10% in the boundary layer is equivalent to an increase of 20% in the mid-troposphere. While the impact of humidity variation on stratiform precipitation persists throughout the 36-h forecast period, the impact diminishes after 24 h in the convective rainfall area. Increasing the boundary layer humidity by 30% leads to a 6 h earlier initiation of convection and a five times larger precipitation amount in the convective area, whereas it is doubled in the stratiform region. These results indicate that accurate measurements of humidity in the boundary layer are most important for QPF.

TOWARDS A GRID INFRASTRUCTURE FOR HYDRO-METEOROLOGICAL RESEARCH

The Distributed Research Infrastructure for Hydro-Meteorological Study (DRIHMS) is a coordinatedaction co-funded by the European Commission. DRIHMS analyzes the main issuesthat arise when designing and setting up a pan-European Grid-based e-Infrastructure for researchactivities in the hydrologic and meteorological fields. The main outcome of the projectis represented first by a set of Grid usage patterns to support innovative hydro-meteorologicalresearch activities, and second by the implications that such patterns define for a dedicatedGrid infrastructure and the respective Grid architecture.