No abstract is provided for this article.
No abstract is provided for this article.
No abstract is provided for this article.
A detailed analysis has been made of a quasi-biennial oscillation (QBO) in the tropospheric ultralong waves of the Southern Hemisphere and interrelationships with the QBO in zonal mean westerly winds of the equatorial stratosphere. In spite of the fact that highly significant spectral peaks at a period close to 26 months occur in both phenomena, results of cross-spectral analysis reveal that the two QBO's are unrelated. The manner in which these QBO's relate to a recently discovered QBO in the 500 mb zonal mean westerly winds throughout the Southern Hemisphere is also considered.
This article briefly summarizes my views that have formed in recent years on communicating climate change in the light of first hand experiences in so-called “climategate”. latter term refers to the emails and personal information about individuals, including me, that were illegally taken from the University of East Anglia through a hacking incident. material published relates to the work of the globallyrespected Climatic Research Unit (CRU) and other scientists around the world. selective publication of some stolen emails taken out of context and distorted is mischievous and cannot be considered a genuine attempt to engage with the climate change issue in a responsible way. Instead there should be condemnation of the abuse, misuse and downright lies about the emails: that should be the real climategate! I was involved in just over 100 of the hacked email messages. In my case, one cherry-picked email quote went viral and at one point it was featured in over 110,000 items (in Google). Here is the quote: The fact is that we can't account for the lack of warming at the moment and it is a travesty that we can't. It is amazing to see this particular quote lambasted so often. It stems from a paper I published bemoaning our inability to effectively monitor the energy flows associated with short-term climate variability. It is quite clear from the paper that I was not questioning the link between anthropogenic greenhouse gas emissions and warming, or even suggesting that recent temperatures are unusual in the context of short-term natural variability. But that is the way a vast majority of the internet stories and blogs interpreted it.
The atmospheric and ocean environment has changed from human activities in ways that affect storms and extreme climate events. The main way climate change is perceived is through changes in extremes because those are outside the bounds of previous weather. The average anthropogenic climate change effect is not negligible, but nor is it large, although a small shift in the mean can lead to very large percentage changes in extremes. Anthropogenic global warming inherently has decadal time scales and can be readily masked by natural variability on short time scales. To the extent that interactions are linear, even places that feature below normal temperatures are still warmer than they otherwise would be. It is when natural variability and climate change develop in the same direction that records get broken. For instance, the rapid transition from El Niño prior to May 2010 to La Niña by July 2010 along with global warming contributed to the record high sea surface temperatures in the tropical Indian and Atlantic Oceans and in close proximity to places where record flooding subsequently occurred. A commentary is provided on recent climate extremes. The answer to the oft-asked question of whether an event is caused by climate change is that it is the wrong question. All weather events are affected by climate change because the environment in which they occur is warmer and moister than it used to be.
An analysis has been made of the spatial and frequency dependence of transient eddy statistics in the Southern Hemisphere at 500 mb. This study emphasizes summer versus winter differences in order to complement previous results of Trenberth (1981), which are shown to nearly correspond to the mean of the summer plus winter statistics. Variance fields of geopotential height, the north–south and east–west geostrophic velocity components, the transient kinetic energy and the poleward transient eddy momentum flux have been analyzed for nine winter and eight summer 128-day seasons from 1972–80. The fields are examined in the frequency domain using Lorenz' (1979) “poor man's spectral analysis” technique. The total fields and the contributions from two broad frequency bands covering periods of 2–8 and 8–64 days are geographically mapped and their zonal means are presented. The spatial distribution of the eddy statistics is quite similar in summer and winter, although the variances in winter are larger and of broader latitudinal extent, thereby indicating a more vigorous circulation overall than in summer. The seasonal changes in eddy statistics closely follow corresponding changes in the mean westerly wind field and are very small over the Indian Ocean, while the largest changes occur in the Pacific Ocean region. A storm track, as indicated by the high frequency fluctuations, exists in the Indian Ocean along 50°S in both summer and winter. The main low frequency variations including blocking-type phenomena occur south of New Zealand and southeast of South America in both seasons, but with small changes in location. Storms in the Pacific Ocean region have a somewhat longer time scale than over the Indian Ocean. A comparison has been made with results from previous studies and, in particular, with statistics based upon station data analyzed at GFDL. The GFDL analyses produce relatively weaker wind speeds over the data sparse oceans. The variance fields are comparable in magnitude but differ in detail, and the GFDL analyses fail to capture the characteristic patterns in the storm track and blocking regions of the hemisphere.
AbstractA detailed analysis of hourly precipitation from 60°N to 60°S for the covariability is performed at 0.25° resolution using the new CMORPH dataset. For all points, correlations are computed ...
This document presents the large scale water budget statistics of a perturbed input-parameter ensemble of atmospheric model runs. The model is Version 5.1.02 of the Community Atmosphere Model (CAM). These runs are the “C-Ensemble” described by Qian et al., “Parametric Sensitivity Analysis of Precipitation at Global and Local Scales in the Community Atmosphere Model CAM5” (Journal of Advances in Modeling the Earth System, 2015). As noted by Qian et al., the simulations are “AMIP type” with temperature and sea ice boundary conditions chosen to match surface observations for the five year period 2000-2004. There are 1100 ensemble members in addition to one run with default inputparameter values.
Droughts occur naturally, but climate change has generally accelerated the hydrological processes to make them set in quicker and become more intense, with
Possible methods for estimating surface fluxes include (i) use of bulk fluxes and in situ observations, (ii) use of model parameterizations to interpret specified inputs and compute surface fluxes, and (iii) various indirect methods, which rely on the fact that the mass and surface heat, energy, and momentum budgets must balance and so, given computations of all the other components in the various budget equations applied to fields either within the ocean or the atmosphere, fluxes may be inferred as a residual. This paper reviews the third approach using indirect methods and outlines the advantages associated with the use of global atmospheric analyses from four-dimensional data assimilation (4DDA). The time mean increment required in producing analyses in 4DDA is identical to the systematic short-term (6 h) assimilating model forecast error and is most likely due to errors in the model physics. Therefore, the analyses include a desirable fix, which allows the sum of the “physics” to be deduced from “dynamics.” The focus is on the heat and moisture budgets to infer surface heat fluxes and freshwater fluxes, but with the recognition of the need to balance the mass budget as well. The diurnal cycle of the vertically integrated mass budget for July 1985 and January 1996 from National Centers for Environmental Prediction (formerly the National Meteorological Center) reanalyses is presented, revealing the strong semidiurnal tide and highlighting the need for at least four-times-daily data. The new results reveal that gross violations of the mass budget continue to be present, but these can be allowed for. A discussion is given of other sources of errors contributing to the heat and moisture budgets.
The energy budget of the modern-day Southern Hemisphere is poorly simulated in both state-of-the-art reanalyses and coupled global climate models. The ocean-dominated Southern Hemisphere has low surface reflectivity and therefore its albedo is particularly sensitive to cloud cover. In modern-day climates, mainly because of systematic deficiencies in cloud and albedo at mid- and high latitudes, too much solar radiation enters the ocean. Along with too little radiation absorbed at lower latitudes because of clouds that are too bright, unrealistically weak poleward transports of energy by both the ocean and atmosphere are generally simulated in the Southern Hemisphere. This implies too little baroclinic eddy development and deficient activity in storm tracks. However, projections into the future by coupled climate models indicate that the Southern Ocean features a robust and unique increase in albedo, related to clouds, in association with an intensification and poleward shift in storm tracks that is not observed at any other latitude. Such an increase in cloud may be untenable in nature, as it is likely precluded by the present-day ubiquitous cloud cover that models fail to capture. There is also a remarkably strong relationship between the projected changes in clouds and the simulated current-day cloud errors. The model equilibrium climate sensitivity is also significantly negatively correlated with the Southern Hemisphere energy errors, and only the more sensitive models are in the range of observations. As a result, questions loom large about how the Southern Hemisphere will actually change as global warming progresses, and a better simulation of the modern-day climate is an essential first step.
