Inhomogeneous influence of the Atlantic warm pool on United States precipitation

Poster thumbnail
Session III: Weather and climate extremes in the Americas
Institite of Oceanography Shanghai Jiaotong University
NOAA/AOML, University of Miami/CIMAS
University of Miami/CIMAS
On interannual time scales, the warming of the Atlantic warm pool (AWP) is associated with a tripole sea surface temperature (SST) pattern in the North Atlantic and leads to more rainfall in the central and eastern US. On decadal-to-multidecadal time scales, the AWP warming corresponds to a basin-wide warming pattern and results in less precipitation in the central and eastern US. The inhomogeneous relationship between the AWP warming and US rainfall on different time scales is largely due to the sign of mid-latitude SST anomaly. The negative mid-latitude SST anomaly associated with the tripole pattern may enhance the low sea level pressure over the northeastern North American continent and also enhance the barotropic response there of the AWP-induced barotropic Rossby wave. This strengthened low pressure system, which is not exhibited when the warming is basin-wide, results in a different moisture transport variation and thus the rainfall pattern over the United States.
Friday, September 11, 2015

Number of comments:   6


There is no "view poster" button on this one -- Aug 31

Does this imply that climate research could be more fruitful, or more understandable, when cast in the Eulerian space of SST patterns (for example, EOFxPC pairs)? From that viewpoint, perhaps the AWP (area exceeding an arbitrary fixed value) is a peculiar, inconvenient mixture of the more fundamentally real "modes" of variability. Is that the interpretation that is implied here?

Or do you consider the AWP a meaningfully fundamental entity, perhaps in solely oceanographic terms, which then needs translation through the space of patterns or modes that it happens to project onto?

Hi Brian, sorry for late reply as I am in the process of settling down. Yeah, I think the Eulerian space of SST patterns does play a role in regulating air-sea interaction which contribute to the climate. However, it is still not fully understood for the air-sea interaction in the mid and high latitudes. So further research using numerical experiments is needed to strengthen the conclusion.

For the definition of the AWP, I still consider it a meaningfully fundamental entity. Though the variability of the AWP can be projected onto major modes of variability cause it is a part of the tropical Atlantic, the definition of the AWP has its own uniqueness in describing the local ocean state and addressing the impacts of the ocean such as on tropical cyclones when the extratropical influences are not significant.

Hi Brian-
Hailong Liu has not uploaded a poster, yet. Hopefully this will happen soon.

Hi Hailong,
Nice work. The barotropic response to AWP warming is actually a wave train of H L H from the southern US across to northwest Atlantic. So at interannual scales the common signal of precipitation anomalies related to AWP anomalies is of opposite sign between south-central US and northeast US. But from your figures it seems like the precipitation anomalies in central and eastern US are of similar sign?

Hi Vasu, so sorry for late reply. It is not convenient to get the access to the internet these several days. Yeah, the precipitation anomalies in central and eastern US of this study roughly have the same sign. one explanation is that the convergence pattern of moisture transport doesn't follow the wave train due to extratropical influences. Also the historical data used in this study is not elaborative. We are performing a further study based on numerical experiments.