Abstract. Every year, from December to April, anthropogenic haze spreads over most of the North Indian Ocean, and South and Southeast Asia. The Indian Ocean Experiment (INDOEX) documented this Indo-Asian haze at scales ranging from individual particles to its contribution to the regional climate forcing. This study integrates the multiplatform observations (satellites, aircraft, ships, surface stations, and balloons) with one-and fourdimensional models to derive the regional aerosol forcing resulting from the direct, the semidirect and the two indirect effects. The haze particles consisted of several inorganic and carbonaceous species, including absorbing black carbon clusters, fly ash, and mineral dust. The most striking result was the large loading of aerosols over most of the South Asian region and the North Indian Ocean. The January to March 1999 visible optical depths were about 0.5 over most of the continent and reached values as large as 0.2 over the equatorial Indian ocean due to long-range transport. The aerosol layer extended as high as 3 km. Black carbon contributed about 14% to the fine particle mass and 11% to the visible optical depth. The single-scattering albedo estimated by several independent methods was consistently around 0.9 both inland and over the open ocean. Anthropogenic sources contributed as much as 80% (_+10%) to the aerosol loading and the optical depth. The in situ data, which clearly support the existence of the first indirect effect (increased aerosol concentration producing more cloud drops with smaller effective radii), are used to develop a composite indirect effect scheme. The Indo-Asian aerosols impact the radiative forcing through a complex set of heating (positive forcing) and cooling (negative forcing) processes. Clouds and black carbon emerge as the major players. The dominant factor, however, is the large negative forcing (-20 +_ 4 W m -t) at the surface and the comparably large atmospheric heating. Regionally, the absorbing haze decreased the surface solar radiation by an amount comparable to 50% of the total ocean heat flux and nearly doubled the lower tropospheric solar heating. We demonstrate with a general circulation model how this additional heating significantly perturbs the tropical rainfall patterns and the hydrological cycle with implications to global climate.

We report the detection of deuterium absorption at redshift 2.525659 toward Q1243+3047. We describe improved methods to estimate the deuterium to hydrogen abundance ratio (D/H) in absorption systems, including improved modeling of the continuum level, the Ly forest, and the velocity structure of the absorption. Together with improved relative flux calibration, these methods give D=H ¼ 2:42 À0:38 Â 10 À5 , from the log D/H-values toward five QSOs. The dispersion in the five values is larger than we expect from their individual measurement errors, and we suspect this is because some of these errors were underestimated. We observe a trend in D/H with log N H i that we also suspect is spurious. The best value for D/H is 0.6 smaller than we quoted in O'Meara et al. from three QSOs, and although we have more values, the error is similar because the dispersion is larger. In standard big bang nucleosynthesis (SBBN), the best D/H corresponds to a baryon-to-photon ratio ¼ 5:9 AE 0:5 Â 10 À10 and gives precise predictions for the primordial abundances of the other light nuclei. We predict more 4 He than is reported in most measurements, although not more than allowed by some estimates of the systematic errors. We predict a 3 He abundance very similar to that reported by Bania et al., and we predict 3-4 times more 7 Li than is seen in halo stars. It is unclear if those stars could have destroyed this much of their 7 Li. The -value from D/H corresponds to a cosmological baryon density b h 2 ¼ 0:0214 AE 0:0020 (AE9.3%), which agrees with the WMAP value of b h 2 ¼ 0:0224 AE 0:001.

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