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Lau, K.-M.

Publications and source records attributed to Lau, K.-M..

76 records · Page 5

Short-term climate variability and atmospheric teleconnections from satellite-observed outgoing longwave radiation. I Simultaneous relationships. II - Lagged correlations

Attention is given to the low-frequency variability of outgoing longwave radiation (OLR) fluctuations, their possible correlations over different parts of the globe, and their relationships with teleconnections obtained from other meteorological parameters, for example, geopotential and temperature fields. Simultaneous relationships with respect to the Southern Oscillation (Namais, 1978; Barnett, 1981) signal and the reference OLR fluctuation over the equatorial central Pacific are investigated. Emphasis is placed on the relative importance of the Southern Oscillation (SO) signal over preferred regions. Using lag cross-correlation statistics, possible lagged relationships between the tropics and midlatitudes and their relationships with the SO are then investigated. Only features that are consistent with present knowledge of the dynamics of the system are emphasized. Certain features which may not meet rigorous statistical significance tests but yet are either expected a priori from independent observations or are predicted from dynamical theories are also explored.

Lau, K.-M.↗

Short-term planetary-scale interactions over the tropics and midlatitudes. II - Winter-MONEX period

The FGGE/winter-Monex wind data from 850 and 200 mb are used to analyze the short-term teleconnections over the tropical and midlatitude Pacific and monsoonal surges in the winter of 1978-79. The data were taken twice a day, and included the total wind field, the computed rotational and divergent winds, the velocity potential, and the streamfunction. Cold surges were identified from shipboard data over the South China Sea and characterized an increase in the surface northerly wind and a surface pressure differential between Hong Kong and 30 deg N, 115 deg E. Midlatitude baroclinic disturbances triggered the cold surges, which displayed intensities dependent on the strength of the midlatitude anticyclogenesis and the intensity of the East Asia local Hadley cell. Fluctuations in the 200 mb jet streak over Japan indicated changes in eddy behavior over the North Pacific and the intensity of the East Asia local Hadley cell circulation and tropical convection. It was concluded that midlatitude synoptic systems could force equatorial convection that produces remote midlatitude responses.

Lau, K.-M.↗

Equatorial response to northeasterly cold surges as inferred from satellite cloud imagery

Daily convective activity in equatorial regions during Dec.-Jan., 1974-1975 was estimated from NOAA satellite data and composited in relation to the phase of cold surge episodes which then occured. Eastward and westward propagating cloud clusters displayed phase speeds of about 5 and 10 m/sec, respectively, and were generated near southwestern Borneo after a cold surge. Kelvin wave responses were indicated by confinement of the eastward-moving components to the equatorial region. Further, an analysis of symmetric and asymmetric characteristics showed that components symmetric with respect to the equator displayed a larger response amplitude, which was taken to mean that strongly trapped waves were generated from heat sources near the equator.

Lau, K.-M.↗