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Latest  publications

1. M. M. Lam and B. A. Tinsley, Solar wind-atmospheric electricity-cloud microphysics connection to weather and climate, Journal of Atmospheric and Solar-Terrestrial Physics, http://dx.doi.org/ 10.1016/ j.jastp.2015. 10.019, 2015.

 

Mai Mai Lam and Brian Tinsley (University of Texas, Dallas) review the large-scale day-to-day dynamic tropospheric responses to changes in the downward current density of the global atmospheric circuit. We discuss recent papers looking at the following responses: the Mansurov effect, the Roberts effect, the Veretenenko effect, the Wilcox effect and the Burns effect.

 

It is available to download from Mai's researchgate page.

 

The review is in a special issue of the Journal of Atmospheric and Solar Terrestrial Physics which is part of the output of the ISSI project "Effects of Interplanetary Disturbances on the Earth’s Atmosphere and Climate"  http://www.issibern.ch/teams/interplanetarydisturb/.

 

 

2. M. J. Owens, C. J. Scott, A. J. Bennett, S. R. Thomas, M. Lockwood, R. G. Harrison, M. M. Lam,   Lightning as a space-weather hazard: UK thunderstorm activity modulated by the passage of the heliospheric current sheet, Geophysical Research Letters, DOI: 10.1002/2015GL066802, 2015.

 

Abstract

 

Lightning flash rates, RL, are modulated by co-rotating interaction regions (CIRs) and the polarity of the heliospheric magnetic field (HMF) in near-Earth space. As the HMF polarity reverses at the heliospheric current sheet (HCS), typically within a CIR, these phenomena are likely related. In this study, RL is found to be significantly enhanced at the HCS and at 27 days prior/after. The strength of the enhancement depends on the polarity of the HMF reversal at the HCS. Near-Earth solar and galactic energetic particle fluxes are also ordered by HMF polarity, though the variations qualitatively differ from RL, with the main increase occurring prior to the HCS crossing Thus the CIR effect on lightning is either the result of compression/amplification of the HMF (and its subsequent interaction with the terrestrial system), or that energetic particle preconditioning of the Earth system prior to the HMF polarity change is central to solar wind-lightning coupling mechanism.

 

 

3. M. M. Lam, G. Chisham and M. P. Freeman, Solar-wind-driven geopotential height anomalies originate in the Antarctic lower troposphere, GRL, 41, doi:10.1002/2014GL061421, 2014.

 

The paper has been published online on the Geophysical Research Letters website in the 28 September issue. It is available to download from Mai's researchgate page.

 

Abstract

 

We use NCEP/NCAR reanalysis data to estimate the altitude and timelag dependence of the correlation between the interplanetary magnetic field component, By, and the geopotential height anomaly above Antarctica. The correlation is most statistically significant within the troposphere.The peak in the correlation occurs at greater timelags at the tropopause (~ 6 − 8 days) and in the mid-troposphere (~ 4 days), than in the lower troposphere (~ 1 day).

 

This supports a mechanism involving the action of the global atmospheric electric circuit, modified by variations in the solar wind, on lower tropospheric clouds. The increase in timelag with increasing altitude is consistent with the upward propagation by conventional atmospheric processes of the solar-wind-induced variability in the lower troposphere. This is in contrast to the downward propagation of atmospheric effects to the lower troposphere from the stratosphere due to solar-variability-driven mechanisms involving ultra-violet radiation or energetic particle precipitation.

 

Some results

 

Figure 3 (right): The Mansurov effect is confined to the

troposphere and the base of the stratosphere in

Antarctica. The results are suggestive of an upward

propagation of the Mansurov effect from the lower to

the upper troposphere.

 

(a) the difference in the 1999-2002 Antarctic field mean in

geopotential height anomaly between IMF By greater than

or equal to 3 nT and IMF By less than or equal to -3 nT

states. A minimum (winter) pressure level for the Antarctic

tropopause of 230 hPa is marked by the horizontal grey

dashed line. A maximum (summer) pressure level for the

Antarctic tropopause is 330 hPa.

 

(b) as for (a) but masked at the 1% field significance level.

The effect is of statistically-significant amplitude within the

troposphere and the base of the stratosphere at the 1% field

significance levels. At any given pressure level, the peak

correlation occurs for positive timelag consistent with

solar-wind-driven ionospheric electric field fluctuations

leading the atmospheric response.

 

(c) The results in (a) are plotted at different pressure levels

with a 3 m offset between each decreasing pressure level

to help with visualization. Statistically-significant values at

the 1% level are plotted in black and values of less statistical significance are plotted in orange. Starting with the line plotted at the bottom of the panel, the levels plotted are 1000, 925, 850, 700, 600, 500, 400, 300 and 250 hPa. The temporally broad peak shifts to increased timelags with increasing altitude, suggestive of an upward propagation of

the Mansurov effect from the lower to the upper troposphere.

 

 

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