Understanding and modeling the fundamental processes that govern
the large precipitation variability and extremes in the western U.S. is a critical test for the ability of climate models to predict the regional water cycle, including floods and droughts.
Not exact matches
Because of
large natural
variability, the first approach results in an outcome suggesting that it is appropriate to conclude that there is no increase in
precipitation by human influences, although the correct interpretation is that there is simply not enough evidence (not a long enough time series).
On decadal time scales, annual streamflow variation and
precipitation are driven by
large - scale patterns of climate
variability, such as the Pacific Decadal Oscillation (see teleconnections description in Climate chapter)(Pederson et al. 2011a; Seager and Hoerling 2014).
Holden, Z. A., Morgan, P., Crimmins, M. A., Steinhorst, R. K. & Smith, A. M. S. Fire season
precipitation variability influences fire extent and severity in a
large southwestern wilderness area, United States.
My experience with extremes and detection and attribution of an anthropogenic signal in those is that only by averaging the behavior of extremes (both temperature extremes and
precipitation extremes) over
large geographical areas (continental or barely sub-continental) we have been able to see something outside of natural
variability.
In part because of
large intrinsic
variability, no evidence was found for changes in extreme
precipitation attributable to climate change in the available observed record.»
So: The study finds a fingerprint of anthropogenic influences on
large scale increase in
precipitation extremes, with remaining uncertainties — namely that there is still a possibility that the widespread increase in heavy
precipitation could be due to an unusual event of natural
variability.The intensification of extreme rainfall is expected with warming, and there is a clear physical mechanism for it, but it is never possible to completely separate a signal of external forcing from climate
variability — the separation will always be statistical in nature.
No changes in extreme
precipitation attributable to climate change were found for the observational period, in
large part because of significant year - to - year
variability.
Its six chapters cover temperature assessment,
precipitation assessment,
large - scale climate
variability modes and related oscillation indices, extreme events, climate and composition of the atmosphere and cryosphere and sea level.
«One of the major modes of climate
variability is El Niño and when we're in El Niño there's a
large area of warm sea surface temps in the Pacific,» this leads to more
precipitation on the West Coast, Crouch said.
It is important to note that RMSE tends to increase with
variability, as illustrated at some locations closer to the equator that tend to have higher
precipitation magnitudes (and
variability) and therefore
larger differences between RMSE and MAE (Figure 1).
Precipitation has much
larger spatial and temporal
variability than temperature, and it is therefore more difficult to identify the impact it has on changes in many systems.
Importantly, the changes in cereal yield projected for the 2020s and 2080s are driven by GHG - induced climate change and likely do not fully capture interannual
precipitation variability which can result in
large yield reductions during dry periods, as the IPCC (Christensen et al., 2007) states: ``... there is less confidence in the ability of the AOGCMs (atmosphere - ocean general circulation models) to generate interannual
variability in the SSTs (sea surface temperatures) of the type known to affect African rainfall, as evidenced by the fact that very few AOGCMs produce droughts comparable in magnitude to the Sahel droughts of the 1970s and 1980s.»
The climate and hence
precipitation variability in northern Africa can be quite
large.
The greater increases in erosion in the GGa1 scenario was attributed to greater
variability in monthly
precipitation and an increased frequency of
large storms in the model simulation.
The robustly project increased moisture flux convergence and
precipitation in the pan-Arctic region over the 21st century, as did their AR4 counterparts (Kattsov et al., 2007; Rawlins et al., 2010 Then we get: since nearly all models project a
large precipitation increase rising above the
variability year - round, it is likely the pan-Arctic region will experience a statistically - significant increase in
precipitation by mid-century.
The
large interannual to decadal hydroclimatic
variability in winter
precipitation is highly influenced by sea surface temperature (SST) anomalies in the tropical Pacific Ocean and associated changes in
large - scale atmospheric circulation patterns [16].
Intraseasonal
precipitation variability on Kilimanjaro and the East African region and its relationship to the
large - scale circulation.
Instrumental records have shown that hydroclimatic
variability across the American Southwest is mostly structured around cool - season
precipitation regimes, with a few winter storms typically contributing a disproportionately
large amount of the annual
precipitation across this region [15].
These aspects of
precipitation generally exhibit
large natural
variability, and El Niño and changes in atmospheric circulation patterns such as the North Atlantic Oscillation have a substantial influence.
But given what is known, he said «there is every reason to believe that the trend toward greater
variability,
larger anomalies, is true for
precipitation as well as temperature.»