Sensibilidad de la convección resuelta hacia las superficies oceánica y terrestres en el Atlántico tropical y la cuenca amazónica

Descargue el texto completo en el repositorio institucional de la Universität Hamburg: http://hdl.handle.net/21.11116/0000-0009-F864-FLos modelos climáticos tienden a representar incorrectamente la lluvia tropical, así como sus interacciones con la superficie debido a su baja resolución espacial que imposibilita resolver procesos de convección. En esta tesis doctoral se investiga la sensibilidad de la convección resuelta hacia su superficie para escalas de tiempo estacionales sobre el océano y diurnas sobre el continente. Sobre el océano, se analiza la interacción de la convección resuelta y la temperatura de la superficie del mar (TSM) relacionada con el Modo Meridional Atlántico (MMA). Se demuestra que la respuesta de la precipitación al MMA en simulaciones desacopladas con convección explícita (E-CON) y parametrizada (P-CON) puede interpretarse como un desplazamiento meridional de la precipitación de aproximadamente 1 grado. Sobre el continente, se investiga si las mejoras en la representación de la precipitación en E-CON pueden atribuirse a la representación de sistemas convectivos organizados (SCO) en la cuenca amazónica. Identificamos que la distribución de la intensidad de la precipitación y el ciclo diurno son las mejoras más importantes en la representación de la precipitación. La precipitación asociada a SCO muestra picos de precipitación nocturna entre 1h-6h, lo que permite representar una distribución espacial heterogénea en el ciclo diurno como en las observaciones.Surface interactions modulate precipitating convection in the tropics. However, convective parameterizations fail in representing tropical precipitation and its interactions with the surface. In recent years, the increased use of "storm-resolving" simulations has shown promising improvements on the simulation of precipitation. In this dissertation, we investigate the sensitivity of resolved convection to its underlying surface from seasonal timescales over ocean to diurnal variations over land in the tropical Atlantic sector. Over ocean, we tackle the interaction of resolved convection and the sea surface temperature (SST) related to the Atlantic Meridional Mode (AMM) with uncoupled and coupled simulations. We investigate whether the explicit representation of convection leads to i) a robust precipitation response to the AMM and ii) a weaker coupling with SST in contrast to simulations that parameterize convection. We show that the precipitation response to the AMM can be interpreted as a meridional shift of the mean-state precipitation towards the warmer hemisphere. Simulations with explicit (E-CON) and parameterized (P-CON) convection exhibit a similar shift, of about 1 , despite of their distinct mean-state precipitation. In contrast, E-CON exhibits stronger mean-state surface winds which translates into greater wind-driven latent heat flux, and can potentially produce stronger changes in the SST anomalies. We test this hypothesis with coupled simulations. Both the precipitation and SST anomalies respond differently to the AMM during its decay from May to July. In May, the shift of the mean-state precipitation in E-CON is consistent with the uncoupled simulations demonstrating a robust precipitation response to the AMM; whereas the P-CON simulations exhibit a displacement of 2 . Moreover, the cooling of SST is stronger in E-CON than in P-CON. This is influenced by wind-driven latent heat flux anomalies, which are larger in E-CON and lead to a stronger cooling by 0.5 to 1.5K. The wind-driven latent heat flux explains a significant part of the total SST cooling in E-CON (67%) as compared to P-CON (48%), which agrees with the proposed hypothesis. Over land, we investigate whether improvements in the representation of precipitation with explicit convection can be attributed to the representation of organized convective systems in the Amazon. We identify that the distribution of precipitation intensity and the diurnal cycle are the precipitation features with major improvements by the E-CON simulations. Light and high intensity precipitation rates are particularly well reproduced by E-CON, whereas they remain biased in P-CON. The E-CON simulations, unlike P-CON, also reproduce the heterogeneous times of maximum precipitation, with most regions featuring their maximum rain in the afternoon (18h-20h), but others depicting a rain peak overnight. The precipitation associated with organized convective systems display overnight precipitation peaks between 1h-6h in E-CON, which enables the representation of heterogeneous times of maximum precipitation as in observations. Moreover, the simulated diurnal evolution of the size and intensity of organized convective systems is consistent with their observed life cycle. We show that E-CON simulates a realistic diurnal cycle of organized convective systems, which helps to improve the overall representation of the precipitation diurnal cycle

Patrones de circulación atmosférica intraestacionales de macroescala en bajos niveles asociados a lluvias en la cuenca amazónica

Este estudio tiene por objetivo identificar Patrones de Circulación (CPs) de macroescala que sinteticen la variabilidad atmosférica intraestacional en estados de circulación recurrentes y reconocibles, en la Cuenca Amazónica (CA). Para ello, se utilizaron vientos diarios del reanálisis ERA-Interim para el periodo 1979-2014. Adicionalmente, se asoció dichos CPs a la lluvia en toda la CA utilizando datos de precipitación basados en observaciones y datos estimados de alta resolución de los productos 3B42 (~25 Km) y 2A25 (~5 Km) del TRMM. Se identificaron 9 CPs utilizando un método híbrido que combina la técnica de redes neuronales (Self-Organizing Maps) y la Clasificación Ascendente Jerárquica. Los CPs muestran un ciclo temporal definido consituaciones alternativas y una duración de 14 días en promedio. Estos describen perturbación estropicales y extratropicales que dirigen inicialmente vientos del norte y posteriormente del sur, hacia el norte o este de la CA. La lluvia asociada concuerda con la dinámica de los vientos y muestra anomalías positivas (negativas) ubicadas en el sur (norte) de la CA que se desplazan progresivamente hacia el norte (sur) o este (oeste). Estos resultados muestran consistencia entre la base de datos de precipitación de HYBAM y TRMM. Por otro lado, se analizaron las características de los CPs durante los eventos de sequía extrema de 1998, 2005 y 2010. Se encontró que dichos eventos pueden ser explicados por la frecuencia de ciertos CPs u otros factores (ej. Variables termodinámicas) que influyen en las características de la lluvia. Los resultados de este estudio abren nuevas perspectivas en cuanto al estudio de la circulación atmosférica intraestacional, considerando el uso de CPs como herramienta para el pronóstico de eventos hidrológicos extremos.This study aims to identify large scale Circulation Patterns (CPs) that summarize the atmospheric intraseasonal variability in some recognizable and recurring circulation situations in the Amazon Basin (AB). Daily low-level winds from ERA-Interim reanalysis for the period 1979-2014, were used to determine the CPs. In addition, to associate these CPs with rainfall in the whole AB, observational data of precipitation and high-resolution dataset from TRMM 3B42 (~ 25 Km) and2A25 (~ 5 Km) products were used. Nine CPs where found using a hybrid method, which combine a neural network technique (Self-Organizing Maps) and the Hierarchical Ascendant Classification. CPs show a defined temporal cycle with alternative situations and a duration of 14 days on average. They describe tropical and extratropical perturbations that lead initially northerly winds to southerlies towards the north or east part of the AB. The related rainfall reveals consistent association with the CPs and shows positive (negative) anomalies located in the south(north) part of the AB that goes gradually to the north (south) and east (west). These results demonstrate good agreement in the three rainfall datasets. Furthermore, we examine the performance of these CPs during 1998, 2005 and 2010 extreme droughts. We found that these events could be explained by the frequency of certain CPs or other factors (e.g. thermodynamic variables) that drive the rainfall characteristics. The results of this research allow to further the intraseasonal atmospheric studies, regarding the use of CPs as a tool of hydrological extreme events forecasting.TesisUniversidad Nacional Agraria La Molina. Facultad de Ciencias. Departamento Académico de Ingeniería Ambiental, Física y Meteorologí

Intra-seasonal rainfall variability in the Amazon basin related to large-scale circulation patterns: a focus on western Amazon-Andes transition region

This study aims to relate the intra-seasonal rainfall variability over the Amazon basin to atmospheric circulation patterns (CPs), with particular attention to extreme rainfall events in the Amazon–Andes region. The CPs summarize the intra-seasonal variability of atmospheric circulation and are defined using daily low-level winds from the ERA-Interim (1.5° × 1.5°) reanalysis for the 1979–2014 period. Furthermore, observational data of precipitation and high-resolution TRMM 3B42 (∼25 km), 2A25 PR (∼5 km) and CHIRPS (∼5 km) data products are related to the CPs throughout the Amazon basin. Nine CPs are determined using a hybrid method that combines a neural network technique (self-organizing maps, SOM) and hierarchical ascendant classification. The CPs are characterized by a specific cycle with alternative transitions and a duration of 14 days on average. This configuration initially results in northerly winds to southerly winds towards the northern or eastern Amazon basin. The related rainfall suggests that it is driven mainly by CP dynamics. In addition, we demonstrate a good agreement amongst the four rainfall data sets: observed precipitation, TRMM 3B42, TRMM 2A25 PR and CHIRPS. Furthermore, special attention is given to the Amazon–Andes transition region. Over this region, two particular CPs (CP4 and CP5) are identified as the key contributors of maximum and minimum daily rainfall, respectively. Thus, during the dry season, 40.8% (11.4%) of the CP5 (CP4) days demonstrate rainfall of less than 1 mm day−1, while during the wet season, 6.2% (14.6%) of the CP5 (CP4) days show rainfall amounts higher than the seasonal 90th percentile (10.4 mm day−1). This study provides additional information concerning the intra-seasonal circulation variability in Amazonia and demonstrates the value of using remote sensing precipitation data in this region as a tool for forecast in areas lacking observable information

Simulated Tropical Precipitation Assessed across Three Major Phases of the Coupled Model Intercomparison Project (CMIP)

The representation of tropical precipitation is evaluated across three generations of models participating in phases 3, 5, and 6 of the Coupled Model Intercomparison Project (CMIP). Compared to state-of-the-art observations, improvements in tropical precipitation in the CMIP6 models are identified for some metrics, but we find no general improvement in tropical precipitation on different temporal and spatial scales. Our results indicate overall little changes across the CMIP phases for the summer monsoons, the double-ITCZ bias, and the diurnal cycle of tropical precipitation. We find a reduced amount of drizzle events in CMIP6, but tropical precipitation occurs still too frequently. Continuous improvements across the CMIP phases are identified for the number of consecutive dry days, for the representation of modes of variability, namely, the Madden-Julian oscillation and El Nino-Southern Oscillation, and for the trends in dry months in the twentieth century. The observed positive trend in extreme wet months is, however, not captured by any of the CMIP phases, which simulate negative trends for extremely wet months in the twentieth century. The regional biases are larger than a climate change signal one hopes to use the models to identify. Given the pace of climate change as compared to the pace of model improvements to simulate tropical precipitation, we question the past strategy of the development of the present class of global climate models as the mainstay of the scientific response to climate change. We suggest the exploration of alternative approaches such as high-resolution storm-resolving models that can offer better prospects to inform us about how tropical precipitation might change with anthropogenic warming

ICON-Sapphire: simulating the components of the Earth system and their interactions at kilometer and subkilometer scales

International audienceState-of-the-art Earth system models typically employ grid spacings of O(100 km), which is too coarse to explicitly resolve main drivers of the flow of energy and matter across the Earth system. In this paper, we present the new ICON-Sapphire model configuration, which targets a representation of the components of the Earth system and their interactions with a grid spacing of 10 km and finer. Through the use of selected simulation examples, we demonstrate that ICON-Sapphire can (i) be run coupled globally on seasonal timescales with a grid spacing of 5 km, on monthly timescales with a grid spacing of 2.5 km, and on daily timescales with a grid spacing of 1.25 km; (ii) resolve large eddies in the atmosphere using hectometer grid spacings on limited-area domains in atmosphere-only simulations; (iii) resolve submesoscale ocean eddies by using a global uniform grid of 1.25 km or a telescoping grid with the finest grid spacing at 530 m, the latter coupled to a uniform atmosphere; and (iv) simulate biogeochemistry in an ocean-only simulation integrated for 4 years at 10 km. Comparison of basic features of the climate system to observations reveals no obvious pitfalls, even though some observed aspects remain difficult to capture. The throughput of the coupled 5 km global simulation is 126 simulated days per day employing 21 % of the latest machine of the German Climate Computing Center. Extrapolating from these results, multi-decadal global simulations including interactive carbon are now possible, and short global simulations resolving large eddies in the atmosphere and submesoscale eddies in the ocean are within reach

ICON-Sapphire: simulating the components of the Earth system and their interactions at kilometer and subkilometer scales

International audienceState-of-the-art Earth system models typically employ grid spacings of O(100 km), which is too coarse to explicitly resolve main drivers of the flow of energy and matter across the Earth system. In this paper, we present the new ICON-Sapphire model configuration, which targets a representation of the components of the Earth system and their interactions with a grid spacing of 10 km and finer. Through the use of selected simulation examples, we demonstrate that ICON-Sapphire can (i) be run coupled globally on seasonal timescales with a grid spacing of 5 km, on monthly timescales with a grid spacing of 2.5 km, and on daily timescales with a grid spacing of 1.25 km; (ii) resolve large eddies in the atmosphere using hectometer grid spacings on limited-area domains in atmosphere-only simulations; (iii) resolve submesoscale ocean eddies by using a global uniform grid of 1.25 km or a telescoping grid with the finest grid spacing at 530 m, the latter coupled to a uniform atmosphere; and (iv) simulate biogeochemistry in an ocean-only simulation integrated for 4 years at 10 km. Comparison of basic features of the climate system to observations reveals no obvious pitfalls, even though some observed aspects remain difficult to capture. The throughput of the coupled 5 km global simulation is 126 simulated days per day employing 21 % of the latest machine of the German Climate Computing Center. Extrapolating from these results, multi-decadal global simulations including interactive carbon are now possible, and short global simulations resolving large eddies in the atmosphere and submesoscale eddies in the ocean are within reach

ICON-Sapphire: simulating the components of the Earth system and their interactions at kilometer and subkilometer scales

International audienceState-of-the-art Earth system models typically employ grid spacings of O(100 km), which is too coarse to explicitly resolve main drivers of the flow of energy and matter across the Earth system. In this paper, we present the new ICON-Sapphire model configuration, which targets a representation of the components of the Earth system and their interactions with a grid spacing of 10 km and finer. Through the use of selected simulation examples, we demonstrate that ICON-Sapphire can (i) be run coupled globally on seasonal timescales with a grid spacing of 5 km, on monthly timescales with a grid spacing of 2.5 km, and on daily timescales with a grid spacing of 1.25 km; (ii) resolve large eddies in the atmosphere using hectometer grid spacings on limited-area domains in atmosphere-only simulations; (iii) resolve submesoscale ocean eddies by using a global uniform grid of 1.25 km or a telescoping grid with the finest grid spacing at 530 m, the latter coupled to a uniform atmosphere; and (iv) simulate biogeochemistry in an ocean-only simulation integrated for 4 years at 10 km. Comparison of basic features of the climate system to observations reveals no obvious pitfalls, even though some observed aspects remain difficult to capture. The throughput of the coupled 5 km global simulation is 126 simulated days per day employing 21 % of the latest machine of the German Climate Computing Center. Extrapolating from these results, multi-decadal global simulations including interactive carbon are now possible, and short global simulations resolving large eddies in the atmosphere and submesoscale eddies in the ocean are within reach