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首页> 外文期刊>Journal of Advances in Modeling Earth Systems >The impact of the diurnal cycle on the propagation of Madden?￠????Julian Oscillation convection across the Maritime Continent
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The impact of the diurnal cycle on the propagation of Madden?￠????Julian Oscillation convection across the Maritime Continent

机译：昼夜周期对马德琳？朱利安涛动对流在海事大陆传播的影响

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摘要

Influences of the diurnal cycle on the propagation of the Madden?￠????Julian Oscillation (MJO) convection across the Maritime Continent (MC) are examined using cloud?￠????permitting regional model simulations and observations. A pair of ensembles of control (CONTROL) and no?￠????diurnal cycle (NODC) simulations of the November 2011 MJO episode are performed. In the CONTROL simulations, the MJO signal is weakened as it propagates across the MC, with much of the convection stalling over the large islands of Sumatra and Borneo. In the NODC simulations, where the incoming shortwave radiation at the top of the atmosphere is maintained at its daily mean value, the MJO convection signal propagating across the MC is enhanced. Examination of the surface energy fluxes in the simulations indicates that the surface downwelling shortwave radiation is larger in the presence of the diurnal cycle (CONTROL simulations) primarily because clouds preferentially form in the afternoon and are smaller during day time in comparison to nighttime. Furthermore, the diurnal covariability of surface wind speed and skin temperature results in a larger sensible heat flux and a cooler land surface in the CONTROL runs compared to NODC runs. An analysis of observations indicates that ahead of and behind the MJO active phase, the diurnal cycle of cloudiness enhances downwelling shortwave radiation and hence convection over the MC islands. This enhanced stationary convection competes with and disrupts the convective signal of MJO events that propagate over the waters surrounding the islands.
机译：利用云区域允许的区域模型模拟和观测，研究了昼夜周期对马登-朱利安对流（MJO）对流在海事大陆（MC）上传播的影响。进行了2011年11月MJO情节的一对控制合奏（CONTROL）和无昼夜循环（NODC）模拟。在CONTROL仿真中，MJO信号在MC上传播时减弱，大部分对流在苏门答腊和婆罗洲的大岛上停滞。在NODC模拟中，大气顶部的短波辐射保持在其每日平均值，从而增强了在MC上传播的MJO对流信号。在模拟中对表面能通量的检查表明，在存在昼夜周期的情况下，地面向下的短波辐射较大（CONTROL模拟），这主要是因为云优先在下午形成，而白天则比夜间小。此外，与NODC运行相比，CONTROL运行中表面风速和皮肤温度的日协变性导致更大的显热通量和凉爽的陆地表面。对观测结果的分析表明，在MJO活跃期之前和之后，乌云密布的昼夜周期增强了下行波的短波辐射，从而增强了MC岛上的对流。这种增强的固定对流与MJO事件的对流信号竞争，并破坏了MJO事件的对流信号，这些事件在岛屿周围的水域上传播。

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