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Large-scale moisture in the climate system and models

Global energy and water cycle components contain considerable uncertainties but global constraints can be used to refine estimates over land, deduce ocean heat and water transports as residuals, and establish errors. [more]

Tropical cyclones and climate

Causes of changes in tropical cyclones have been explored in several studies. Trenberth and Shea (2006) analyzed the origins of the record breaking 2005 Atlantic hurricane season. [more]

The vertical temperature structure of the atmosphere

An analysis (Trenberth and Smith 2006) was performed of the full three-dimensional spatial structure of the temperature field monthly mean anomalies from ERA-40 for a core region of the tropics from 30?N to 30?S, with results projected globally using regression. [more]

Climate variability and observations

As part of a special issue of the J. Climate arising from the June 2004 CLIVAR science conference, current and past members of the Atlantic Implementation Panel of International CLIVAR, completed a comprehensive review of three interrelated climate phenomena: Tropical Atlantic variability (TAV), the North Atlantic Oscillation (NAO), and the Atlantic Meridional Overturning Circulation (MOC) (Hurrell et al. 2006a). [more]

Diagnostic analyses of extratropical ocean-atmosphere-sea ice variability using models and observations

Using suites of atmospheric general circulation model (AGCM) simulations forced by global, regional, and idealized sea surface temperature (SST) variations Hoerling et al. (2006) found that multi-decadal variations and trends in SSTs have determined the spatial patterns, time history and seasonality of observed changes in African rainfall since 1950. [more]

Climate forcings

An analysis of results from a suite of 12 state-of-the-art climate models show that ocean warming and sea-level rise in the twentieth century were substantially reduced by the colossal eruption in 1883 of the volcano Krakatoa in Indonesia (Gleckler et al 2006). Volcanically induced cooling of the ocean surface penetrated into deeper layers, where it persisted for decades after the event. [more]

IPCC fourth assessment

A major project has been development of the IPCC AR4 report, and Chapter 3 of WG I, in particular (Trenberth et al. 2007). Not only has Trenberth led this effort, but several CAS personnel, D. Shea, J. Hurrell, C. Deser, J. Fasullo and A. Dai, are listed as contributing authors, and many of the figures were developed by Shea and Trenberth. [more]

Additional Information

References

Figure 1. (High resolution image) Hydrological cycle. The hydrological cycle. Estimates of the main water reservoirs, given in plain font in 103 km3, and the flow of moisture through the system, given in slant font in103 km3/yr, equivalent to Exagrams (1018 g) per year. (Trenberth et al. 2006a).

Figure 2. (High resolution image) Hurricane Katrina Hours 42-54. For 1800 UTC 28 August to 0600 UTC 29 August 2005, hours 42 to 54 of the simulation, given are (left) the azimuthally-averaged precipitation (mm/h), and (right) column integrated moisture convergence and surface latent heat flux as a function of radius for the control (red) and changes in SST of +1ºC (blue) and -1ºC (green). The precipitation and latent heat fluxes are area averages from the eye to the radius plotted to be compatible with the moisture convergence across that cylinder radius. (Trenberth et al. 2006b).

Figure 3. (High resolution image) Yearly Surface Hurricane Flux. Based on best track data for the tropical cyclones observed each year classified by maximum wind speed, the total surface energy loss by the global ocean is given based on Katrina simulated fluxes within 400 km of the eye of the storms as given by (2) as latent (blue), sensible (cyan) and total enthalpy (black) flux in 1021 Joules per year. Also given in green (right hand scale) is the precipitation in the same units. The dotted lines are linear trends. Trenberth et al (2006c).

Figure 4. (High resolution image) Annual-mean frequency and intensity of daily precipitation. Annual-mean frequency (% of time, left column) and intensity (mm/day, right column) of daily precipitation (>1 mm/day) events from TRMM satellite observations (top panels, 3B42 data set, 1998-2003 mean) and four different coupled models (1991-2000 mean). From Dai 2006a. Note the underestimates of intensity and overestimates of frequency of precipitation in the models.

Figure 5. (High resolution image) 1950-1999 trends. The 1950-1999 trends in observed (left), GOGA (middle), and Indian Ocean forced (right) FMA rainfall (mm). The observed trend (gray bar) and PDFs of 50-yr rainfall trends averaged over the indicated region are shown in far right panel. The red (black) curve is from 80 (60) individual members of the GOGA (Indian Ocean) runs. The blue curve is from 15 members of unforced coupled model simulations.

Figure 6. (High resolution image) ENSO event anomaly composites of precipitation. Warm – cold ENSO event anomaly composites of precipitation during DJF for CAM3 (top) and CMAP (bottom). The contours are 0.25, 0.5, 1, 2, 4, and 8 mm day-1.