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The frequency of cloud detection and the frequency with which these clouds are found in the upper troposphere have been extracted from NOAA High Resolution Infrared Radiometer Sounder (HIRS) polar-orbiting satellite data from 1979 to 2001. The HIRS/2 sensor was flown on nine satellites from the Television Infrared Observation Satellite-Next Generation (TIROS-N) through NOAA-14, forming a 22-yr record. Carbon dioxide slicing was used to infer cloud amount and height. Trends in cloud cover and high-cloud frequency were found to be small in these data. High clouds show a small but statistically significant increase in the Tropics and the Northern Hemisphere. The HIRS analysis contrasts with the International Satellite Cloud Climatology Project (ISCCP), which shows a decrease in both total cloud cover and high clouds during most of this period.

[1] To generate a climatologically homogenized time series of the upper tropospheric water vapor (UTWV), intersatellite calibration is carried out for 3 decades of High-Resolution Infrared Radiation Sounder (HIRS) channel 12 clear-sky measurements. Because of the independence of the individual satellite's instrument calibration, intersatellite biases exist from satellite to satellite. To minimize the expected intersatellite biases, measurement adjustments are derived from overlapping HIRS data from the equator to the poles to account for the large global temperature observation range. Examination of the intersatellite biases shows that the biases are scene temperature-dependent. Many overlapping satellites have bias variations of more than 0.5 K across the scene temperature ranges. An algorithm is developed to account for the varying biases with respect to brightness temperature. Analyses based on the intercalibrated data show that selected regions of UTWV are highly correlated with low-frequency indexes such as the Pacific Decadal Oscillation index and the Pacific and North America index, especially in the winter months. The derived upper tropospheric humidity in the central Pacific also corresponds well with the Niño 3.4 index. Thirty year trend analysis indicates an increase of upper tropospheric humidity in the equatorial tropics. The areal coverage of both high and low humidity values also increased over time. These features suggest the possibility of enhanced convective activity in the tropics.

Research and forecasts of the weather‐ocean‐climate system demand increasingly higher resolution forcing data. Here we assess the improvement in composite global observations and the feasibility of producing high resolution blended sea winds. The number of the long‐term US sea surface wind speed observing satellites has increased from one in July 1987 to five or more since 2000. Global 0.25° gridded, blended products with temporal resolutions of 6‐hours, 12‐hours and daily have become feasible since mid 2002, mid 1995 and January 1991, respectively (with ≥75% time coverage and ≥90% spatial coverage between 65°S–65°N). If the coverage is relaxed, the feasible times can be extended to earlier periods. These statistics provide practical guidance to produce reliable blended products for different applications, and serve as guidance on the design of future global observing systems.