Convective signals from surface measurements at ARM Tropical Western Pacific site: Manus

Journal Article · Fri Feb 04 04:00:00 EST 2011 · Climate Dynamics, 36(3-4):431-449

DOI:https://doi.org/10.1007/s00382-009-0736-z· OSTI ID:1004802

Wang, Yi; Long, Charles N; Mather, James H; Liu, Xiaodong

Madden-Julian Oscillation (MJO) signals have been detected using highly sampled observations from the U.S. DOE ARM Climate Research Facility located at the Tropical Western Pacific Manus site. Using downwelling shortwave radiative fluxes and derived shortwave fractional sky cover, and the statistical tools of wavelet, cross wavelet, and Fourier spectrum power, we report finding major convective signals and their phase change from surface observations spanning from 1996 to 2006. Our findings are confirmed with the satellite-gauge combined values of precipitation from the NASA Global Precipitation Climatology Project and the NOAA interpolated outgoing longwave radiation for the same location. We find that the Manus MJO signal is weakest during the strongest 1997-1998 El Nin˜o Southern Oscillation (ENSO) year. A significant 3-5-month lead in boreal winter is identified further between Manus MJO and NOAA NINO3.4 sea surface temperature (former leads latter). A striking inverse relationship is found also between the instantaneous synoptic and intraseasonal phenomena over Manus. To further study the interaction between intraseasonal and diurnal scale variability, we composite the diurnal cycle of cloudiness for 21-MJO events that have passed over Manus. Our diurnal composite analysis of shortwave and longwave fractional sky covers indicates that during the MJO peak (strong convection), the diurnal amplitude of cloudiness is reduced substantially, while the diurnal mean cloudiness reaches the highest value and there are no significant phase changes. We argue that the increasing diurnal mean and decreasing diurnal amplitude are caused by the systematic convective cloud formation that is associated with the wet phase of the MJO, while the diurnal phase is still regulated by the well-defined solar forcing. This confirms our previous finding of the anti-phase relationship between the synoptic and intraseasonal phenomena. The detection of theMJOover the Manus site provides further opportunities in using other ground-based remote sensing instruments to investigate the vertical distributions of clouds and radiative heatings of the MJO that currently is impossible from satellite observations.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1004802
• Report Number(s): PNNL-SA-70955; KP1701000
• Journal Information: Climate Dynamics, 36(3-4):431-449, Journal Name: Climate Dynamics, 36(3-4):431-449 Journal Issue: 3-4 Vol. 36; ISSN CLDYEM; ISSN 0930-7575
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
AMPLITUDES
CLIMATES
CLOUDS
CONVECTION
DETECTION
DOWNWELLING
NASA
OSCILLATIONS
PRECIPITATION
RADIATIONS
REMOTE SENSING
SATELLITES
SEAS
SKY
SOUTHERN OSCILLATION