A study of the global distribution of the various cloud types and their seasonal and diurnal variations, as well as a study of how clouds have changed in the past half-century, are underway. Databases are being created that are designed to be useful in clarifying the interactions of clouds with other components of the climate system and to infer changes in cloud radiative forcing. For global-change studies involving clouds, a long period of record with global coverage and with consistent observing procedures is necessary. Routine surface weather observations of clouds from land stations and from ships in the ocean meet these requirements.
Under two previous NSF grants the PIs have produced a climatology of cloud-type amounts for 5-degree and 10-degree grid boxes, seasonally and monthly, for eight times per day for the years 1952-1997 over the oceans and 1971-1996 over land. For this renewed research project, both databases will be updated with cloud observations for the decade 1997-2006. Arrangements will also be made for continuation of routine updating of the cloud-observations database for the ocean after termination of this project.
The analysis of interannual variations and trends for land and ocean will be updated to 2006. A number of studies will be done to examine characteristics of the data: describing diurnal cycles, comparing day trends to night trends, comparing island observations to those of nearby ships, quantifying uncertainties in regional and global time-series, investigating interannual variations and trends of Arctic clouds, and determining the relation of cloud base height to sea-surface temperature.
Broader impact: The broader impact of the research is in the area of climate research. The databases produced under this project will be distributed widely for use by the scientific community. They will find applications in climate modeling, cloud process studies, and in detection and attribution of climate change.
