Zonal mean wind, the Indian monsoon, and July drying in the western Atlantic subtropics

Kelly, Patrick; Mapes, Brian E.

doi:10.1029/2010jd015405

Cited by 31 publications

(30 citation statements)

References 49 publications

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“…The variation of the NASH intensity and its western ridge is mainly due to dynamical processes such as monsoon circulations and the associated diabatic heating (Rodwell and Hoskins 2001;Cook et al 2008;Kelly and Mapes 2011;L. Li et al 2012;.…”

Section: Discussionmentioning

confidence: 99%

“…Global warming and changes in the NASH western ridge D13 claimed that global warming has not caused the western ridge to move westward since there is not a significant negative correlation between global surface temperature and western-ridge longitude during 1948-2010. It is important to recognize that the changes of the NASH intensity and its western ridge are mainly determined by dynamical effects (Rodwell and Hoskins 2001;Cook et al 2008;Kelly and Mapes 2011;L. Li et al 2012;; the relationship between the ridge and global mean temperature does not have to be linear.…”

Section: -Yr Periodmentioning

confidence: 99%

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Reply to “Comments on ‘Changes to the North Atlantic Subtropical High and Its Role in the Intensification of Summer Rainfall Variability in the Southeastern United States’”

et al. 2013

Journal of Climate

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Recently Diem questioned the western ridge movement of the North Atlantic subtropical high (NASH) reported in a 2011 paper of Li et al. This reply shows more analysis that further strengthens the conclusions originally put forth by Li et al. Diem's analysis of the trend in the western ridge of the NASH was based on the data over a 30-yr period , whereas the main conclusions in Li et al. were drawn according to the data over a 60-yr period . Over the last 60 years, the NASH has shown a significant trend of westward movement, the meridional movement of the western ridge of the NASH has enhanced in the recent three decades, and the potential impact of global warming cannot be ruled out in an attempt to explain these changes of the NASH.

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Section: Discussionmentioning

confidence: 99%

Section: -Yr Periodmentioning

confidence: 99%

Reply to “Comments on ‘Changes to the North Atlantic Subtropical High and Its Role in the Intensification of Summer Rainfall Variability in the Southeastern United States’”

et al. 2013

Journal of Climate

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“…4), which is often called the Caribbean low-level jet. It has a similar but even more pronounced seasonality within the Caribbean Sea (Small et al 2007;Muñoz et al 2008) and coincides with an increase of the surface pressure gradients as the North Atlantic subtropical high extends farther westward (Kelly and Mapes 2011;Muñoz et al 2008).…”

Section: A Atmospheric Structure and Large-scale Forcingsmentioning

confidence: 91%

On the Seasonal and Synoptic Time-Scale Variability of the North Atlantic Trade Wind Region and Its Low-Level Clouds

Brueck

Nuijens

Stevens

2015

Journal of the Atmospheric Sciences

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The seasonality in large-scale meteorology and low-level cloud amount (CC low ) is explored for a 58 3 58 area in the North Atlantic trades, using 12 years of ERA-Interim and MODIS data, supported by 2 years of Barbados Cloud Observatory (BCO) measurements. From boreal winter to summer, large-scale subsiding motion changes to rising motion, along with an increase in sea surface temperature, a clockwise turning and weakening of low-level winds, and reduced cold-air advection, lower-tropospheric stability (LTS), and surface fluxes. However, CC low is relatively invariant around 30%, except for a minimum of 20% in fall. This minimum is only pronounced when MODIS scenes with large high-level cloud amount are excluded, and a winter maximum in CC low is more pronounced at the BCO. On monthly time scales, wind speed has the best correlation with CC low . Existing large-eddy simulations suggest that the wind speed-CC low correlation may be explained by a direct deepening response of the trade wind layer to stronger winds. Large correlations of wind direction and advection with CC low also suggest that large-scale flow patterns matter. Smaller correlations with CC low are observed for LTS and surface evaporation, as well as negligible correlations for relative humidity (RH) and vertical velocity. However, these correlations considerably increase when only summer is considered. On synoptic time scales, all correlations drop substantially, whereby wind speed, RH, and surface sensible heat flux remain the leading parameters. The lack of a single strong predictor emphasizes that the combined effect of parameters is necessary to explain variations in CC low in the trades.

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“…The lack of linear correlation between the anomalous SST modes and the westward shift of the NASH is consistent with mechanisms that have been suggested by previous studies to contribute to the westward shift of the NASH. For example, Kelly and Mapes (2011) show that this westward expansion is a result of the dynamic response of zonal wind to the change of diabatic heating of the Asian monsoon. Cook et al (2008) suggest that the westward expansion in a warmer climate is a result of stronger warming of land surface relative to that of the ocean.…”

Section: Conclusion and Discussionmentioning

confidence: 98%

Decadal Variation of Rainfall Seasonality in the North American Monsoon Region and Its Potential Causes

Arias

2012

Journal of Climate

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This study shows that the North American monsoon system's (NAMS) strength, onset, and retreat over northwestern Mexico exhibit multidecadal variations during the period 1948-2009. Two dry regimes, associated with late onsets, early retreats, and weaker rainfall rates, occurred in 1948-70 and 1991-2005, whereas a strong regime, associated with early onsets, late retreats, and stronger rainfall rates, occurred in 1971-90. A recovery of the monsoon strength was observed after 2005. This multidecadal variation is linked to the sea surface temperature anomalies' (SSTAs) variability, which is a combination of the Atlantic multidecadal oscillation (AMO) and the warming SST trends. These SST modes appear to cause an anomalous cyclonic circulation and enhanced rainfall over the southeastern United States and the Gulf of Mexico, which in turn increases the atmospheric stability over the monsoon region. However, these SST modes cannot fully explain the circulation and rainfall anomalies observed during the early-retreat monsoons. An expansion of the North Atlantic surface high (NASH) in recent decades also contributes to the anomalous circulation associated with the early retreats of the NAMS. A northwestward expansion of the NASH further enhances the anomalous cyclonic circulation and rainfall over the southeastern United States and the Gulf of Mexico. Its associated northwestward shift of the subtropical jets over the western United States enhances subsidence over the NAMS region. The combined effects of the AMO, the warming trends, and the NASH expansion on atmospheric circulation contribute to a stronger and more persistent earlier retreat during the recent dry regime (1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005), while the earlier dry regime appears to be only influenced by the positive phase of the AMO.

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Zonal mean wind, the Indian monsoon, and July drying in the western Atlantic subtropics

Cited by 31 publications

References 49 publications

Reply to “Comments on ‘Changes to the North Atlantic Subtropical High and Its Role in the Intensification of Summer Rainfall Variability in the Southeastern United States’”

Reply to “Comments on ‘Changes to the North Atlantic Subtropical High and Its Role in the Intensification of Summer Rainfall Variability in the Southeastern United States’”

On the Seasonal and Synoptic Time-Scale Variability of the North Atlantic Trade Wind Region and Its Low-Level Clouds

Decadal Variation of Rainfall Seasonality in the North American Monsoon Region and Its Potential Causes

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