Evaporation measurements with an Optical-Microwave Scintillometer system over a Saline lake in the Atacama Desert

2020 ◽  
Author(s):  
Felipe Lobos Roco ◽  
Oscar Hartogensis ◽  
Jordi Vila ◽  
Alberto de la Fuente ◽  
Francisco Suarez
Keyword(s):  
Large Scale ◽  
Saline Lake ◽  
Regional Scale ◽  
Atacama Desert ◽  
Open Water ◽  
Heat Fluxes ◽  
Sudden Increase ◽  
Surface Heat Fluxes ◽  
Advantages And Disadvantages ◽  
Water Outflow

<p>Evaporation is the main water outflow and a key component of the water and surface energy balance in the endorheic basins of the Atacama Desert. This is very localized to confined environments such as saline lakes, wetlands and crop fields. In these environments, the understanding of evaporation is challenging due to the interaction between the large-scale forcing and local scale turbulence over heterogeneous surfaces. Here, the advection of momentum, heat or moisture plays an important role in the enhancement of evaporation. To understand the evaporation dynamics over such environments, we performed a comprehensive 10-days experiment: the E-DATA (<strong>E</strong>vaporation caused by <strong>D</strong>ry <strong>A</strong>ir <strong>T</strong>ransport over the <strong>A</strong>tacama Desert), localized under extreme conditions in the Salar del Huasco saline lake (22,3°S - 68,8°W - 3790 m a.s.l.), Chile. The measurement strategy was based on spatially distributed high-resolution surface and airborne observations in combination with WRF (Weather Research Forecasting) modeling. The main findings of the experiment show that evaporation is mainly controlled by the lack of turbulence in the morning and by regional-scale forcing in the afternoon, which leads to a sudden increase in mechanical turbulence, therefore in the evaporation flux.  </p><p>This work compares two in-situ independent measurements of surface heat fluxes over the saline lake, by using an Eddy Covariance (EC) system and an Optical-Microwave Scintillometer (OMS). Our results show in general a good agreement between EC and OMS measurements of latent (L<sub>v</sub>E) and sensible (H) heat fluxes over the water surface (R<sup>2</sup>: 0,90-0,96). During the morning, slight differences are observed between the EC and OMS measurements. However, differences up to 200 W m<sup>-2</sup> are observed in the afternoon for L<sub>v</sub>E and up to 20 Wm<sup>-2</sup> for H. The first analysis shows that these differences given during the afternoon are likely attributed to Monin-Obukhov stability (MOST) functions, which need to be developed yet for open water surfaces. Moreover, differences in the footprint of both measurement systems together with dramatic wind changes between the morning and afternoon may play a role. Finally, inaccurate bandpass filtering of the raw scintillometer signal may be a factor in the differences between EC and OMS, where we are currently working to refine our results. Our findings highlight the advantages and disadvantages of each measurement method over an open water body and provide a discussion about its performance.    </p>

scholarly journals Simulating carbon exchange using a regional atmospheric model coupled to an advanced land-surface model

2008 ◽  
Vol 5 (5) ◽  
pp. 4161-4207 ◽  
Author(s):  
H. W. Ter Maat ◽  
R. W. A. Hutjes
Keyword(s):  
Carbon Dioxide ◽  
Land Surface ◽  
Large Scale ◽  
Regional Scale ◽  
Atmospheric Model ◽  
Surface Fluxes ◽  
Heat Fluxes ◽  
Surface Model ◽  
Carbon Exchange ◽  
Regional Atmospheric Modelling System

Abstract. A large scale mismatch exists between our understanding and quantification of ecosystem atmosphere exchange of carbon dioxide at local scale and continental scales. This paper will focus on the carbon exchange on the regional scale to address the following question: What are the main controlling factors determining atmospheric carbon dioxide content at a regional scale? We use the Regional Atmospheric Modelling System (RAMS), coupled with a land surface scheme simulating carbon, heat and momentum fluxes (SWAPS-C), and including also sub models for urban and marine fluxes, which in principle include the main controlling mechanisms and capture the relevant dynamics of the system. To validate the model, observations are used which were taken during an intensive observational campaign in the central Netherlands in summer 2002. These included flux-site observations, vertical profiles at tall towers and spatial fluxes of various variables taken by aircraft. The coupled regional model (RAMS-SWAPS-C) generally does a good job in simulating results close to reality. The validation of the model demonstrates that surface fluxes of heat, water and CO2 are reasonably well simulated. The comparison against aircraft data shows that the regional meteorology is captured by the model. Comparing spatially explicit simulated and observed fluxes we conclude that in general simulated latent heat fluxes are underestimated by the model to the observations which exhibit large standard deviation for all flights. Sensitivity experiments demonstrated the relevance of the urban emissions of carbon dioxide for the carbon balance in this particular region. The same test also show the relation between uncertainties in surface fluxes and those in atmospheric concentrations.

scholarly journals Interannual Agulhas Leakage Variability and Its Regional Climate Imprints

2018 ◽  
Vol 31 (24) ◽  
pp. 10105-10121 ◽  
Author(s):  
Yu Cheng ◽  
Lisa M. Beal ◽  
Ben P. Kirtman ◽  
Dian Putrasahan
Keyword(s):  
Time Scales ◽  
Large Scale ◽  
Regional Climate ◽  
Austral Summer ◽  
Heat Fluxes ◽  
Convective Rainfall ◽  
Surface Heat Fluxes ◽  
Model Studies ◽  
Large Scale Field ◽  
The Indian Ocean

We investigate the interannual variability of Agulhas leakage in an ocean-eddy-resolving coupled simulation and characterize its influence on regional climate. Many observational leakage estimates are based on the study of Agulhas rings, whereas recent model studies suggest that rings and eddies carry less than half of leakage transport. While leakage variability is dominated by eddies at seasonal time scales, the noneddy leakage transport is likely to be constrained by large-scale forcing at longer time scales. To investigate this, leakage transport is quantified using an offline Lagrangian particle tracking approach. We decompose the velocity field into eddying and large-scale fields and then recreate a number of total velocity fields by modifying the eddying component to assess the dependence of leakage variability on the eddies. We find that the resulting leakage time series show strong coherence at periods longer than 1000 days and that 50% of the variance at interannual time scales is linked to the smoothed, large-scale field. As shown previously in ocean models, we find Agulhas leakage variability to be related to a meridional shift and/or strengthening of the westerlies. High leakage periods are associated with east–west contrasting patterns of sea surface temperature, surface heat fluxes, and convective rainfall, with positive anomalies over the retroflection region and negative anomalies within the Indian Ocean to the east. High leakage periods are also related to reduced inland convective rainfall over southeastern Africa in austral summer.

scholarly journals Enhanced Persistence of Equatorial Waves via Convergence Coupling in the Stochastic Multicloud Model

2015 ◽  
Vol 72 (12) ◽  
pp. 4701-4720 ◽  
Author(s):  
Noah D. Brenowitz ◽  
Yevgeniy Frenkel ◽  
Andrew J. Majda
Keyword(s):  
Large Scale ◽  
Heat Fluxes ◽  
Sea Surface ◽  
Theoretical Studies ◽  
Equatorial Waves ◽  
Moist Convection ◽  
Kelvin Wave ◽  
Surface Heat Fluxes ◽  
Walker Cell ◽  
Conditional Instability

Abstract Recent observational and theoretical studies show a systematic relationship between tropical moist convection and measures related to large-scale convergence. It has been suggested that cloud fields in the column stochastic multicloud model compare better with observations when using predictors related to convergence rather than moist energetics (e.g., CAPE) as per Peters et al. Here, this work is extended to a fully prognostic multicloud model. A nonlocal convergence-coupled formulation of the stochastic multicloud model is implemented without wind-dependent surface heat fluxes. In a series of idealized Walker cell simulations, this convergence coupling enhances the persistence of Kelvin wave analogs in dry regions of the domain while leaving the dynamics in moist regions largely unaltered. This effect is robust for changes in the amplitude of the imposed sea surface temperature (SST) gradient. In essence, this method provides a soft convergence coupling that allows for increased interaction between cumulus convection and the large-scale circulation but does not suffer from the deleterious wave–conditional instability of the second kind (CISK) behavior of the Kuo-type moisture-convergence closures.

Salinity response to atmospheric forcing of the Terra Nova Bay polynya, Antarctica

2021 ◽  
pp. 1-14
Author(s):  
Deborah A. Le Bel ◽  
Christopher J. Zappa ◽  
Giorgio Budillon ◽  
Arnold L. Gordon
Keyword(s):  
Ross Sea ◽  
Open Water ◽  
Heat Fluxes ◽  
Ice Formation ◽  
Atmospheric Forcing ◽  
Surface Heat Fluxes ◽  
Water Fraction ◽  
Salinity Response ◽  
Terra Nova Bay ◽  
Terra Nova

Abstract The density and salinity of High Salinity Shelf Water, a key component of Antarctic Bottom Water emanating from the Ross Sea, are intensified by brine rejection induced by ice formation within the Terra Nova Bay (TNB) polynya. Ocean mooring data from 2007, meteorological observations from automatic weather stations and a satellite-derived history of the opening of TNB polynya delineate variability in water column salinity linked to atmospheric forcing, with a period on the order of 10 days. Lagged correlation analysis indicates that on average salinity response lags the polynya opening by 2 days and the wind forcing by 5 days. We find stronger correlations of salinity with the wind during March through May and with the polynya open-water fraction during June through October, with decreasing lags in the latter period. A one-dimensional mixed-layer model incorporating thermodynamic ice formation captures the oscillations in salinity. A process study shows that the variability in the polynya open-water fraction governs the final salinity attained by the model as well as the salinity cycling. Variability in surface heat fluxes modulates that effect. Our work suggests that there is a more complex relationship between salinity, the polynya open-water fraction, and atmospheric forcing than previously suggested.

scholarly journals The role of large-scale moistening by adiabatic lifting in the Madden-Julian Oscillation convective onset

2021 ◽  
pp. 1-49
Author(s):  
Chelsea E. Snide ◽  
Ángel F. Adames ◽  
Scott W. Powell ◽  
Víctor C. Mayta
Keyword(s):  
Large Scale ◽  
Heat Fluxes ◽  
Data Sets ◽  
Madden Julian Oscillation ◽  
Onset Of Convection ◽  
Surface Heat Fluxes ◽  
Planetary Scale ◽  
Moisture Advection ◽  
The Indian Ocean

AbstractThe initiation of the Madden-Julian Oscillation over the Indian Ocean is examined through the use of a moisture budget that applies a version of the weak temperature gradient (WTG) approximation that does not neglect dry adiabatic vertical motions. Examination of this budget in ERA-Interim reveals that horizontal moisture advection and vertical advection by adiabatic lifting govern the moistening of the troposphere for both primary and successive MJO initiation events. For both types of initiation events, horizontal moisture advection peaks prior to the maximum moisture tendency, while adiabatic lifting peaks after the maximum moisture tendency. Once convection initiates, moisture is maintained by anomalous radiative and adiabatic lifting. Adiabatic lifting during successive MJO initiation is attributed to the return of the circumnavigating circulation from a previous MJO event, while in primary events the planetary-scale circulation appears to originate over South America. Examination of the same budget with data from the DYNAMO northern sounding array shows that adiabatic lifting contributes significantly to MJO maintenance, with a contribution that is comparable to that of surface heat fluxes. However, results from the DYNAMO data disagree with those from ERA-Interim over the importance of adiabatic lifting to the moistening of the troposphere prior to the onset of convection. In spite of these differences, the results from the two data sets show that small departures from WTG balance in the form of dry adiabatic motions cannot be neglected when considering MJO convective onset.

scholarly journals EDITORIAL

2013 ◽  
Vol 31 (2) ◽  
pp. 207
Author(s):  
Jose Antonio Moreira Lima
Keyword(s):  
Data Assimilation ◽  
Atlantic Ocean ◽  
Ocean Circulation ◽  
Large Scale ◽  
Early Stage ◽  
Specific Area ◽  
Heat Fluxes ◽  
Surface Heat Fluxes ◽  
Forecast Models ◽  
Ocean Forecasting

This issue presents a set of papers related to the development of ocean forecasting models with data assimilation skills for the South Atlantic Ocean, more specifically for the Metarea V maritime region whose western border is delimited by the Brazilian shelf. This work has been done with the collaboration of many Brazilian researchers under the Oceanographic Modeling and Observation Network (REMO) research group. The evolution from an early stage of running ocean models with mean climatological forcings aiming at the study of specific oceanographic processes to the present stage of running operational ocean forecast models with synoptic forcings and data assimilation had a strong contribution from researchers with a meteorological background, who brought their expertise on numerical weather forecasting.The papers present distinct topics associated with an ocean forecasting system, such as a detailed description of network design and implementation of the ocean circulation models, a proposed approach of nesting distinct models starting from a large scale Atlantic Ocean grid to regional high-resolution local grids, data assimilation methods, synoptic sea surface fields obtained from remote sensing, surface heat fluxes, and planning observational measurement programs for assimilation and model evaluation.We hope that these papers contribute towards developing this specific area of operational oceanic forecasting within the Brazilian scientific and ocean technology communities. We still have a steady way to follow in order to consolidate and improve the propo-sed initiatives, but the first steps were already given and sound results are now available. In the near future, we foresee continuous improvement of oceanic models and data assimilation methods as well as collaboration with interested researchers from Brazilian and foreign institutions. Jose Antonio Moreira LimaInvited Editor  Este volume apresenta um conjunto de artigos relacionados com o tema previsão oceânica de curto prazo para o Oceano Atlântico Sul, mais especificamente para a região marítima Metarea V, através de modelos numéricos de circulação com assimilação de dados observacionais. Este trabalho está sendo desenvolvido a partir da cooperação de diversos pesquisadores brasileiros colaboradores da Rede de Modelagem e Observação Oceanográfica (REMO). No estudo dos processos oceanográficos, a evolução do estágio de rodar modelos oceânicos utilizando forçantes climatológicas médias para o estágio atual de rodar modelos operacionais com forçantes sinóticas e assimilação de dados teve uma forte contribuição de pesquisadores oriundos da área de meteorologia, que trouxeram seu conhecimento aplicado dos modelos de previsão do tempo.Os artigos abordam diversos tópicos associados com um sistema de previsão oceânica, tais como uma descrição detalhada do projeto e implementação dos modelos de circulação oceânica; aninhamento escalonado de modelos com escalas distintas, a partir de malha computacional do Oceano Atlântico, para malhas regionais com alta resolução espacial; métodos de assimilação de campos e dados observados; campos sinóticos da superfície do mar através sensoriamento remoto; fluxos de calor de superfície; e planejamento de observações para assimilação e avaliação dos modelos.Desejamos que estes artigos contribuam para desenvolvimento desta área específica de previsão oceânica operacional junto às comunidades científica e de tecnologia oceânica brasileira. Temos ainda um extenso caminho pela frente para consolidar e aperfeiçoar as iniciativas propostas, mas os primeiros passos foram dados e bons resultados já estão disponíveis. Para o futuro, vislumbramos aprimoramento contínuo dos modelos oceânicos e métodos de assimilação de dados, assim como a colaboração com pesquisadores interessados de instituições brasileiras ou estrangeiras. Jose Antonio Moreira LimaEditor Convidado 

scholarly journals Tropical Transition of the 2001 Australian Duck

2010 ◽  
Vol 138 (6) ◽  
pp. 2038-2057 ◽  
Author(s):  
Luke Andrew Garde ◽  
Alexandre Bernardes Pezza ◽  
John Arthur Tristram Bye
Keyword(s):  
Potential Vorticity ◽  
Large Scale ◽  
Three Dimensional ◽  
Vertical Wind Shear ◽  
Heat Fluxes ◽  
Pressure System ◽  
Surface Heat Fluxes ◽  
Warm Core ◽  
Tasman Sea ◽  
Upper Level

Abstract In March 2001, a hybrid low pressure system, unofficially referred to as Donald (or the Duck), developed in the Tasman Sea under tropical–extratropical influence, making landfall on the southeastern Australian coast. Here, it is shown that atmospheric blocking in the Tasman Sea produced a split in the subtropical jet, allowing persistent weak vertical wind shear to manifest in the vicinity of the developing low. It is hypothesized that this occurred through sustained injections of potential vorticity originating from higher latitudes. Hours before landfall near Byron Bay, the system developed an eye with a short-lived warm core at 500 hPa. Cyclone tracking revealed an erratic track before the system decayed and produced heavy rains and flash flooding. A three-dimensional air parcel backward-trajectory scheme showed that the air parcels arriving in the vicinity of the mature cyclone originated from tropical sources at lower levels and from the far extratropics at higher levels, confirming the hybrid characteristics of this cyclone. A high-resolution (0.15°) nested simulation showed that recent improvements in the assimilation scheme used by the Australian models allowed for accurately simulating the system’s trajectory and landfall, which was not possible at the time of the event. Compared to the first South Atlantic hurricane of March 2004, the large-scale precursors were similar; however, the Duck was exposed to injections of upper-level potential vorticity and favorable surface heat fluxes for a shorter period of time, resulting in it achieving partial tropical transition only hours prior to landfall.

scholarly journals A New Evapotranspiration Model Accounting for Advection and Its Validation during SMEX02

2013 ◽  
Vol 2013 ◽  
pp. 1-13 ◽  
Author(s):  
Yongmin Yang ◽  
Hongbo Su ◽  
Renhua Zhang ◽  
Jianjun Wu ◽  
Jianwei Qi
Keyword(s):  
Regional Scale ◽  
Local Scale ◽  
Heat Fluxes ◽  
Stress Index ◽  
Coefficient Of Determination ◽  
Remotely Sensed Data ◽  
Crop Water Stress Index ◽  
Scale Evaluation ◽  
Surface Heat Fluxes ◽  
Water Stress Index

Based on the crop water stress index (CWSI) concept, a new model was proposed to account for advection to estimate evapotranspiration. Both local scale evaluation with sites observations and regional scale evaluation with a remote dataset from Landsat 7 ETM+ were carried out to assess the performance of this model. Local scale evaluation indicates that this newly developed model can effectively characterize the daily variations of evapotranspiration and the predicted results show good agreement with the site observations. For all the 6 corn sites, the coefficient of determination (R2) is 0.90 and the root mean square difference (RMSD) is 58.52W/m2. For all the 6 soybean sites, theR2and RMSD are 0.85 and 49.46W/m2, respectively. Regional scale evaluation shows that the model can capture the spatial variations of evapotranspiration at the Landsat-based scale. Clear spatial patterns were observed at the Landsat-based scale and are closely related to the dominant land covers, corn and soybean. Furthermore, the surface resistance derived from instantaneous CWSI was applied to the Penman-Monteith equation to estimate daily evapotranspiration. Overall, results indicate that this newly developed model is capable of estimating reliable surface heat fluxes using remotely sensed data.

scholarly journals Local evaporation controlled by regional atmospheric circulation in the Altiplano of the Atacama Desert

2021 ◽  
Vol 21 (11) ◽  
pp. 9125-9150
Author(s):  
Felipe Lobos-Roco ◽  
Oscar Hartogensis ◽  
Jordi Vilà-Guerau de Arellano ◽  
Alberto de la Fuente ◽  
Ricardo Muñoz ◽  
...  
Keyword(s):  
Wind Speed ◽  
Pacific Ocean ◽  
Atmospheric Circulation ◽  
Regional Scale ◽  
Atacama Desert ◽  
Sudden Increase ◽  
The Pacific ◽  
Ground Heat Flux ◽  
The Pacific Ocean ◽  
Strong Winds

Abstract. We investigate the influence of regional atmospheric circulation on the evaporation of a saline lake in the Altiplano (also known as the Andean Plateau) region of the Atacama Desert. For that, we conducted a field experiment in the Salar del Huasco (SDH) basin (135 km east of the Pacific Ocean), in November 2018. The measurements were based on surface energy balance (SEB) stations and airborne observations. Additionally, we simulate the meteorological conditions on a regional scale using the Weather Research and Forecasting Model. Our findings show two evaporation regimes: (1) a morning regime controlled by local conditions, in which SEB is dominated by the ground heat flux (∼0.5 of net radiation), very low evaporation (LvE<30 W m−2) and wind speed <1 m s−1; and (2) an afternoon regime controlled by regional-scale forcing that leads to a sudden increase in wind speed (>15 m s−1) and a jump in evaporation to >500 W m−2. While in the morning evaporation is limited by very low turbulence (u*∼0.1 m s−1), in the afternoon strong winds (u*∼0.65 m s−1) enhance mechanical turbulence, increasing evaporation. We find that the strong winds in addition to the locally available radiative energy are the principal drivers of evaporation. These winds are the result of a diurnal cyclic circulation between the Pacific Ocean and the Atacama Desert. Finally, we quantify the advection and entrainment of free-tropospheric air masses driven by boundary layer development. Our research contributes to untangling and linking local- and regional-scale processes driving evaporation across confined saline lakes in arid regions.

Sign in / Sign up

Export Citation Format

Share Document