Simulation of the Indian monsoon using the RegCM3–ROMS regional coupled model

Ratnam, J. V.; Giorgi, Filippo; Kaginalkar, Akshara; Cozzini, Stefano

doi:10.1007/s00382-008-0433-3

Cited by 118 publications

(75 citation statements)

References 41 publications

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“…For example, considering the major influence of SSTs on the climate of the Caribbean and on simulated precipitation, accurate representation of SSTs in the models could improve their performance. The dynamical downscaling using PRECIS RCM uses prescribed SSTs, but a model set-up in which SSTs are allowed to dynamically interact with and respond to changes in the overlaying atmosphere has been shown to perform better at simulating precipitation in other parts of the world (Artale et al, 2009;Ratnam et al, 2009). Such RCM studies are, however, non-existent for the Caribbean region.…”

Section: Summary and Discussionmentioning

confidence: 99%

A review of observed and projected changes in climate for the islands in the Caribbean

Karmalkar¹,

Taylor²,

Campbell³

et al. 2013

Atmósfera

102

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RESUMENLos cambios climáticos observados y proyectados tienen implicaciones socioeconómicas importantes para las islas del Caribe. El objetivo de este artículo es presentar información esencial sobre el cambio climá-tico -basada en estudios previos, observaciones disponibles y simulaciones de modelos climáticos-a escalas espaciales relevantes para las islas caribeñas. Se utilizan datos del modelo general de circulación (GCM) incluidos en el Proyecto de Comparación de Modelos Acoplados fase 3 (CMIP3), así como del modelo climático regional (RCM) del Centro Hadley del Reino Unido, para aportar tanto información actual como información basada en proyecciones sobre precipitaciones y temperatura en estados insulares específicos. Se utilizan observaciones reticuladas de estaciones y datos satelitales para estudiar el clima del siglo XX y evaluar el desempeño de los modelos climáticos. Con un enfoque centrado en la precipitación, también se analizan factores como la temperatura superficial del mar, la presión al nivel del mar y los vientos que influyen en las variaciones estacionales de la precipitación. La media del ensamble del CMIP3 y el RCM captan satisfactoriamente las peculiaridades de la circulación atmosférica de gran escala en la región, pero no así el ciclo estacional bimodal característico de la precipitación. La aridez en épocas de lluvias prevista en escenarios de cambio climático en la región se ha abordado en estudios previos, pero la magnitud de la variación es muy incierta en las simulaciones tanto del GCM como del RCM. La disminución proyectada es mayor al inicio de la temporada de lluvias y suprime la sequía del medio verano en el Caribe occidental. Las simulaciones del RCM muestran avances respecto del GCM, sobre todo por sus mejores representaciones de la extensión territorial, pero su desempeño depende en gran medida de la conducción del GCM. El presente estudio destaca la necesidad de contar con observaciones de alta resolución y comparar simulaciones de modelos climáticos para entender a fondo el cambio climático y su impacto en las pequeñas islas del Caribe. ABSTRACTObserved and projected changes in climate have serious socio-economic implications for the Caribbean islands. This article attempts to present basic climate change information-based on previous studies, available observations and climate model simulations-at spatial scales relevant for islands in the Caribbean. We use the General Circulation Model (GCM) data included in the Coupled Model Intercomparison Project phase 3 (CMIP3) and the UK Hadley Centre regional climate model (RCM) data to provide both present-day and scenario-based future information on precipitation and temperature for individual island states. Gridded station observations and satellite data are used to study 20th century climate and to assess the performance of climate models. With main focus on precipitation, we also discuss factors such as sea surface temperature, sea level pressure and winds that affect seasonal variations in precipitation. The CMIP3 ensemble me...

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Section: Summary and Discussionmentioning

confidence: 99%

A review of observed and projected changes in climate for the islands in the Caribbean

Karmalkar¹,

Taylor²,

Campbell³

et al. 2013

Atmósfera

102

View full text Add to dashboard Cite

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“…In general, these studies reported an improvement in dynamic downscaling due to coupled models. For example, using the coupled RegCM3 and the ocean model ROMS, Ratnam et al (2009) showed that the coupled model captured the main features of the Indian monsoon and simulated a substantially more realistic spatial distribution and monthly mean of monsoon rainfall compared to the uncoupled atmosphere-only model. A more striking feature is that in an East Asian summer monsoon (EASM) downscaling study (Yao and Zhang, 2009), using the coupled RegCM3 with specified SST the simulated correlation coefficients of the temporal variation of summer rainfall between the uncoupled model RegCM3 and observation were only 0.30 and 0.29 over the Yangtze River Valley and South China, respectively.…”

Section: Temporal Variability and Possible Impact Due To Coupled Oceamentioning

confidence: 99%

A review on regional dynamical downscaling in intraseasonal to seasonal simulation/prediction and major factors that affect downscaling ability

Xue

Janjić

Dudhia

et al. 2014

Atmospheric Research

212

135

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Regional climate models (RCMs) have been developed and extensively applied for dynamically downscaling coarse resolution information from different sources, such as general circulation models (GCMs) and reanalyses, for different purposes including past climate simulations and future climate projection. Thus far, the nature, the methods, and a number of crucial issues concerning the use of dynamic downscaling are still not well understood. The most important issue is whether, and if so, under what conditions dynamic downscaling is really capable of adding more information at different scales compared to the GCM or reanalysis that imposes lateral boundary conditions (LBCs) to the RCMs. There are controversies regarding the downscaling ability. In this review paper we present several factors that have consistently demonstrated strong impact on dynamic downscaling ability in intraseasonal and seasonal simulations/predictions and future projection. Those factors include setting of the RCM experiment (e.g. imposed LBC quality, domain size and position, LBC coupling, and horizontal resolution); as well as physical processes, mainly convective schemes and vegetation and soil processes that include initializations, vegetation specifications, and planetary boundary layer and surface coupling. These studies indicate that RCMs have downscaling ability in some aspects but only under certain conditions. Any significant weaknesses in one of these aspects would cause an RCM to lose its dynamic downscaling ability. This paper also briefly presents challenges faced in current RCM dynamic downscaling and future prospective, which cover the application of coupled ocean-atmosphere RCMs, ensemble applications, and future projections.

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“…Interestingly, a very similar type of bias pattern has been found in the superparameterized CAM (SP-CAM) mentioned previously (Khairoutdinov et al 2008), as well as the superparameterized version of the NASA Goddard finite-volume general circulation model (fvGCM; Tao et al 2009). Meanwhile, a positive off-equatorial rain bias has been seen in a number of recent high-resolution (but still not convection-resolving) simulations of the Asian summer monsoon (Cherchi and Navarra 2007;Lau and Ploshay 2009;Nguyen and McGregor 2009;Ratnam et al 2009). Given that this type of bias does not appear as prominently in the conventional versions of the CAM and NASA fvGCM (Khairoutdinov et al 2008;Tao et al 2009), it would seem that the coupling between parameterized convection and the resolved circulation is somehow involved.…”

Section: Space-time Variability Of Rainfallmentioning

confidence: 99%

“…Along these lines, Khairoutdinov et al (2005) showed that the SP-CAM's excessive rainfall in the northwest Pacific could be mitigated by altering the domain configuration of the model's cloud-resolving convective parameterization. Alternatively, Ratnam et al (2009) showed that the positive rainfall bias in their simulations of the Asian summer monsoon could be mitigated by allowing two-way coupling between the ocean and atmosphere. However, this improvement came at the expense of producing a compensating negative bias in the underlying SST (with amplitude of *1°C).…”

Section: Space-time Variability Of Rainfallmentioning

confidence: 99%

Convectively coupled Kelvin and easterly waves in a regional climate simulation of the tropics

2009

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This study evaluates the performance of a regional climate model in simulating two types of synoptic tropical weather disturbances: convectively-coupled Kelvin and easterly waves. Interest in these two wave modes stems from their potential predictability out to several weeks in advance, as well as a strong observed linkage between easterly waves and tropical cyclogenesis. The model is a recent version of the weather research and forecast (WRF) system with 36-km horizontal grid spacing and convection parameterized using a scheme that accounts for key convective triggering and inhibition processes. The domain spans the entire tropical belt between 45°S and 45°N with periodic boundary conditions in the east-west direction, and conditions at the meridional/lower boundaries specified based on observations. The simulation covers 6 years from 2000 to 2005, which is long enough to establish a statistical depiction of the waves through space-time spectral filtering of rainfall data, together with simple lagged-linear regression. Results show that both the horizontal phase speeds and three-dimensional structures of the waves are qualitatively well captured by the model in comparison to observations. However, significant biases in wave activity are seen, with generally overactive easterly waves and underactive Kelvin waves. Evidence is presented to suggest that these biases in wave activity (which are also correlated with biases in time-mean rainfall, as well as biases in the model's tropical cyclone climatology) stem in part from convection in the model coupling too strongly to rotational circulation anomalies. Nevertheless, the model is seen to do a reasonable job at capturing the genesis of tropical cyclones from easterly waves, with evidence for both wave accumulation and critical layer processes being importantly involved.

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Simulation of the Indian monsoon using the RegCM3–ROMS regional coupled model

Cited by 118 publications

References 41 publications

A review of observed and projected changes in climate for the islands in the Caribbean

A review of observed and projected changes in climate for the islands in the Caribbean

A review on regional dynamical downscaling in intraseasonal to seasonal simulation/prediction and major factors that affect downscaling ability

Convectively coupled Kelvin and easterly waves in a regional climate simulation of the tropics

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