Observation of Moisture Tendencies Related to Shallow Convection

Yoneyama, Kunio; Katsumata, Masaki; Nishizawa, Tomoaki; Yasunaga, Kazuaki; Shirooka, Ryuichi

doi:10.1175/jas-d-14-0042.1

Cited by 33 publications

(30 citation statements)

References 69 publications

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“…The fractal dimension of shallow convection (see next) decreases with time as the cloud system organizes but is very high throughout cloud lifetime. This might result in very high stochastic detrainment per unit area which would allow shallow clouds to efficiently moisten the atmosphere [57].…”

Section: Normalizationmentioning

confidence: 99%

Lagrangian Cloud Tracking and the Precipitation-Column Humidity Relationship

Igel

2018

Atmosphere

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Abstract:The tropical, oceanic mean relationship between column relative humidity and precipitation is highly non-linear. Mean precipitation remains weak until it rapidly picks up and grows at high column humidity. To investigate the origin of this relationship, a Lagrangian cloud tracking code, RAMStracks, is developed, which can follow the evolution of clouds. RAMStracks can record the morphological properties of convective clouds, the meteorological environment of clouds, and their effects. RAMStracks is applied to a large-domain radiative convective equilibrium simulation, which produces a complex population of convective clouds. RAMStracks records the lifecycle of 501 clouds through growth, splits, mergers, and decay. The mean evolution of all these clouds is examined. It is shown that the column humidity evolves non-monotonically, but that lower-level and upper-level contributions to total moisture do evolve monotonically. The precipitation efficiency of tropical storms tends to increase with cloud age. This is confirmed using a prototype testing method. The same method reveals that different tracked clouds with similar initial conditions evolve in very different ways. This makes drawing general conclusions from individual storms difficult. Finally, the causality of the precipitation-column humidity relationship is examined. A Granger Causality test, as well as regressions, suggest that moisture and precipitation are causally linked, but that the direction of causality is ambiguous. Much of this link appears to come from the lower-level moisture's contribution to column humidity.

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Section: Normalizationmentioning

confidence: 99%

Lagrangian Cloud Tracking and the Precipitation-Column Humidity Relationship

Igel

2018

Atmosphere

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“…This pattern suggests that the largescale SLP decreases in P1-P3 are mainly due to the weakening and southward shift of the Mascarene High rather than to diabatic heating by convection. The large-scale mean updraft could become large in association with continuous SLP decreases exceeding 10 days and with the moistening of the lower troposphere by shallow convection over a time scale of a few days, which was discussed in preconditioning studies (Waite and Khouider 2010;Masunaga 2013;Bellenger et al 2015), and could be easily and gradually activated under conditions involving continuous SLP decreases.…”

Section: Kinematic and Thermodynamic Structures Of The Mjo At Each Stagementioning

confidence: 99%

Equatorially Antisymmetric Features in the Initiation Processes of the Madden-Julian Oscillation Observed in Late October during CINDY2011

Moteki

2015

Journal of the Meteorological Society of Japan

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In this study, we investigated the equatorially antisymmetric features in the initiation processes of the MaddenJulian oscillation (MJO) event in late October during the cooperative Indian Ocean experiment on intraseasonal variability in the year 2011. This MJO event developed when the thermal equator was drastically shifted from the Northern Hemisphere to the equator from September to October as the Mascarene High over the southern Indian Ocean decayed and shifted southward. The large-scale fields of sea level pressure, temperature, and moisture around the MJO exhibited equatorially antisymmetric features. According to their different features in terms of surface convergence, temperature, and moisture, MJO convection over the Indian Ocean after its onset consisted of four distinct convective components: the southern intertropical convergence zone between 10°S and 0° along the meridional sea surface temperature (SST) gradients (s-ITCZ), the northern-ITCZ at the southern edge of the high SST above 29°C over the Bay of Bengal, the vortex disturbance over the Arabian Sea (VDAS) in association with the zonal SST gradients, and the westward-propagating diurnal convection originating from Sumatra. In particular, the double-ITCZ and VDAS were characterized by a steady, low-level convergence zone along the surface potential temperature gradients forced by the SST. Before the onset of the MJO convection, the double-ITCZ was characterized by cross-equatorial vertical circulation that was baroclinically tilted northward, and s-ITCZ convection was inhibited owing to the strong Mascarene High. After the onset, single, larger-scale upward motion was barotropically formed over the equator because of the equatorward shift of the double-ITCZ. Such changes in the equatorially antisymmetric meridional circulation are relevant for the organization of the MJO convection.

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“…Intensive observations were conducted over the Indian Ocean (hereafter, IO) during the period from 1 October 2011 to 15 January 2012, and a large amount of high-quality data was collected (Ciesielski et al 2014a;Deng et al 2014;Feng et al 2014;Moum et al 2014;Y13). The observations captured many important processes that would be key to a complete understanding of the MJO, such as (1) the deep moistening which led to MJO convective initiation Johnson and Ciesielski 2013;Johnson et al 2015;Y13), (2) the evolution of populations of different cloud types in each stage of the MJO (Bellenger et al 2015;Feng et al 2014;Powell and Houze 2013;Ruppert and Johnson 2015;Zuluaga and Houze 2013;Xu and Rutledge 2014), and (3) the sub-daily to seasonal upper ocean variations Moum et al 2014;Seiki et al 2013;Yokoi et al 2014;Y13).…”

Section: Introductionmentioning

confidence: 99%

“…An emphasis was placed on the significant roles of radiative-convective feedback (e.g., Hu and Randall 1994) for this period (Hannah and Maloney 2014;Johnson et al 2015). While these findings were based on a dense network of observations and simulations, the observed MJO events also posed questions, such as the causality between the shallow/congestus clouds and the subsequent evolution of the MJO-scale deep moistening (e.g., Bellenger et al 2015;Hagos et al 2014b;Powell and Houze 2013;Ruppert and Johnson 2015). Thus, further investigation for this period is still necessary, as well as an exploration of other MJO cases.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of the Near Real-Time Forecasts Using a Global Nonhydrostatic Model during the CINDY2011/DYNAMO

Nasuno

Kikuchi

Nakano

et al. 2017

Journal of the Meteorological Society of Japan

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By comparison with satellite and field observations, the comprehensive performance and potential utility of near real-time forecasts using Nonhydrostatic Icosahedral Atmospheric Model (NICAM) are demonstrated by exploiting the Cooperative Indian Ocean Experiment on Intraseasonal Variability in the Year 2011 (CINDY2011) / Dynamics of the Madden-Julian Oscillation (DYNAMO) campaign. A week-long forecast was run each day using a regionally stretched version of NICAM, with the finest mesh size of 14 km over the tropical Indian Ocean (IO), throughout the intensive observation period (IOP).The simulated precipitation time series fairly represented the evolution and propagation of the observed Madden-Julian Oscillation (MJO) events, although a 30 % overprediction of precipitation over the IO domain (60 -90°E, 10°S -10°N) was found on average. Frequencies of strong (> 40 mm day −1 ) precipitation were overpredicted, while those of weak precipitation were underpredicted against satellite observations. Compared with the field observations at Gan Island, the biases in precipitation frequency were less obvious, whereas the growth of lower to middle tropospheric dry (~ 1 g kg −1) and warm (~ 1 K) biases were found. Despite these mean biases, temporal variations of the moisture and zonal wind profiles including the MJO events were reasonably simulated.Using the forecast data the moisture and energy budgets during the IOP were investigated. The diagnosis using the 7-day-mean fields captured the observed features of the MJO events. Meanwhile, significant upward transport of moisture by the grid-resolved high-frequency variability was detected throughout the IOP. The relationship between these high-frequency effects and the simulated MJO or mean biases is also discussed.

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Observation of Moisture Tendencies Related to Shallow Convection

Cited by 33 publications

References 69 publications

Lagrangian Cloud Tracking and the Precipitation-Column Humidity Relationship

Lagrangian Cloud Tracking and the Precipitation-Column Humidity Relationship

Equatorially Antisymmetric Features in the Initiation Processes of the Madden-Julian Oscillation Observed in Late October during CINDY2011

Evaluation of the Near Real-Time Forecasts Using a Global Nonhydrostatic Model during the CINDY2011/DYNAMO

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