Vertical Temperature Structure Research Articles

Three-Dimensional Structure of Convectively Coupled Equatorial Waves in Aquaplanet Experiments with Resolved or Parameterized Convection

Abstract Accurate simulations of convectively coupled equatorial waves (CCEWs) are key to properly forecasting rainfall and weather patterns within (and outside) the tropics. Many studies have shown that global numerical weather prediction (NWP) models usually do not accurately simulate CCEWs; however, it is unclear if this problem can be alleviated with a better representation of deep convection in the models. To this end, this study investigates the representation of multiple types of CCEWs in the Model for Prediction Across Scales-Atmosphere (MPAS-A). The simulated structure of CCEWs is analyzed from three MPAS-A aquaplanet experiments with horizontal cell spacing of 30, 15, and 3 km, respectively. Using a wave-phase composite technique, the simulated structure is compared against observed CCEWs as represented by satellite and reanalysis data. All aquaplanet experiments capture the overall structure of gravity wave–type equatorial waves (e.g., Kelvin waves and inertio-gravity waves). Those waves are more realistic in the 3-km experiment, particularly in terms of the vertical structure of temperature, water vapor, and wind anomalies associated with the waves. The main reason for this improvement is a more realistic diabatic heating profile; the experiment with resolved convection produces stronger heating (or weaker cooling) below the melting level during the convectively active phase of Kelvin and inertio-gravity waves. Intriguingly, the rainfall and lower-tropospheric structure associated with easterly waves show pronounced discrepancies between the aquaplanet experiments and reanalysis. Resolved deep convection primarily affects the intensity and propagation speeds of these waves.

An idealized sensitivity study of fine particles' impact on the urban vertical temperature structure

Fine particles (PM2.5) scatter and absorb solar radiation affecting the atmospheric temperature structure, and the effects vary with different concentrations and compositions. This study investigated the effect of PM2.5 on the urban temperature structure of Nanjing through concentration- and species-sensitive experiments using a box model. The results show that the optical parameters, atmospheric heating rate, radiative forcing, and temperature are affected by the PM2.5 concentration, PM2.5 composition, and relative humidity. Under 80% relative humidity, the asymmetry and single scattering albedo (SSA) were 0.7 and 0.88, while under 20% relative humidity, they were 0.6 and 0.77, respectively. PM2.5 increased the atmospheric heating rate by 1–18 K/day; while the surface temperature decreased with the presence of PM2.5. Furthermore, the heterogeneous concentration and composition distributions of PM2.5 led to changes in urban heat island (UHI) intensity. The UHI intensity could be reduced by 1–3 K by PM2.5, and the reduction increased with the increase in PM2.5 concentration and absorbing compositions. The existence of absorbing compositions and high concentrations of PM2.5 may work together to mask the UHI effect and other problems of urban development from 2000s till the present.

Representation of the Convectively Coupled Kelvin Waves in Modern Reanalysis Products

Abstract This study aims to deepen our understanding of the destabilization mechanisms and the mean-state modulation of the convectively coupled Kelvin waves (CCKWs) while testing simple models for CCKWs. We examine CCKW precipitation, vertical structure, and energetics in four modern reanalyses: the fifth version of ECMWF Reanalysis (ERA5), NASA Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2), the second version of the NCEP Climate Forecast System Reanalysis (CFSR), and the Japanese 55-year Reanalysis (JRA-55). The CCKW precipitation signal strength in the wavenumber–frequency domain and the geographical distribution of CCKW precipitation variability are reasonably represented in all reanalyses, although they commonly underestimate the amplitude of CCKW precipitation. Despite considerable interreanalysis differences in the vertical structure of temperature and diabatic heating anomalies, the eddy available potential energy (EAPE) generation within the CCKWs is found to be associated with the second baroclinic mode whereas the first baroclinic mode damps CCKW EAPE in three out of four reanalyses. Geographically, strong CCKW activity occurs in the areas of high mean-state sea surface temperature (SST), where the second mode EAPE generation is higher, mainly due to a stronger stratiform heating and a tighter wave–convection coupling. Our results are supportive of the simple models for CCKWs in which CCKWs are destabilized within the second baroclinic mode component.

Ammonia Abundance Derived from Juno MWR and VLA Observations of Jupiter

The vertical distribution of trace gases in planetary atmospheres can be obtained with observations of the atmosphere’s thermal emission. Inverting radio observations to recover the atmospheric structure, however, is nontrivial, and the solutions are degenerate. We propose a modeling framework to prescribe a vertical distribution of trace gases that combines a thermochemical equilibrium model with a vertical temperature structure and compare these results to models where ammonia can vary between predefined pressure nodes. We compare these model to nadir brightness temperatures and limb-darkening parameters, together with their uncertainties, which we reduced from the raw Juno Microwave Radiometer (MWR) data set. We then apply this framework to MWR observations during Juno’s first years of operation (perijove passes 1–12) and to longitudinally averaged latitude scans taken with the upgraded Very Large Array. We use the model to constrain the distribution of ammonia between −60° and 60° latitude and down to 100 bars. We constrain the ammonia abundance to be ppm ( solar abundance) and find a depletion of ammonia down to a depth of ∼20 bars, which supports the existence of processes that deplete the atmosphere below the ammonia and water cloud layers. At the equator we find an increase of ammonia with altitude, while the zones and belts in the midlatitudes can be traced down to levels where the atmosphere is well mixed. The latitudinal variation in the ammonia abundance appears to be opposite to that shown at higher altitudes, which supports the existence of a stacked-cell circulation model.

Observations of Autumnal Cooling in a Large Estuary

AbstractSeasonal variations in solar insolation and wind create an annual water temperature cycle that impacts circulation and biological processes. The waters of Long Island Sound (LIS) warm from March‐February until August‐October and then begin to cool. Ship surveys show that the vertical temperature structure becomes almost uniform during this season when the area experiences low air temperatures and high winds. However, no observations have resolved the temporal evolution of the vertical structure of temperature during these cooling periods because conditions inhibit ship operations. We report glider measurements of the vertical structure of water temperatures and salinities from 22 October to 4 November 2014, in eastern LIS. We find that 20 m of water can cool at approximately during intervals of cold air and strong winds. We use the data to estimate heat content tendencies and infer surface fluxes. We also estimate the surface heat fluxes using buoy‐mounted instruments and show they are consistent. The net heat flux to the atmosphere exceeds 600 W/m2 during the gilder deployment and approximately 66% of this is due to latent heat transfer. Using the buoy fluxes and products of an operation regional model, we show that the agreement with the fluxes derived from heat budget is improved by using local wind observations. In addition to confirming the extremely large cooling rates, our results demonstrate that gliders can be used in a complex region with strong tidal currents to resolve the temperature structure and heat budget during the severe weather of the cooling season.

Types of Severe Convective Wind Events in Eastern Australia

Abstract Severe winds associated with thunderstorms and convection are a hazard affecting key aspects of society, including emergency management and infrastructure design. Several studies around the world have shown that severe convective winds (SCWs) can occur due to several different processes, in a range of atmospheric environments, with significant regional and temporal variations. However, in eastern Australia, the types of SCWs and their variability have not been assessed outside of individual case studies. Here, a combination of reanalysis, lightning, radar, and station data are used to characterize a set of 36 SCW events in four locations in eastern Australia. These events are objectively chosen based on the strongest measured wind gusts from station data (greater than 25 m s−1) over a 14-yr period, with 6-hourly lightning data and a 30-dBZ radar reflectivity threshold used to infer moist convective processes. Radar data analysis suggests that these SCW events are produced by several different types of parent thunderstorms, with station observations suggesting a range of temporal characteristics for these different event types. A clustering algorithm applied to environmental data is used to suggest three dominant types of events, based on low-level moisture, low-level temperature lapse rate, and deep-layer mean wind speed and vertical shear. Based on the distribution of synoptic conditions and thunderstorm properties for each environmental cluster, it is suggested that these three event types correspond to the following: 1) shallow vertical transport of strong synoptic-scale winds to the surface, 2) downbursts driven by subcloud evaporation, and 3) intense thunderstorms including supercells. Significance Statement The purpose of this study is to better understand the different types of severe wind events in eastern Australia that are produced by convective storms. We looked at 36 historical cases in four locations and find that severe winds can be produced by very different classes of convective storms. We also suggest that there are three key types of atmospheric environment that are associated with events in this region. These environments vary in terms of the vertical structure of temperature, moisture, and wind speed above the surface. Understanding the different types of environments that lead to severe convective winds can help to reduce uncertainties in future climate projections for this region based on environmental changes.

Modulation of Upper Ocean Vertical Temperature Structure and Heat Content by a Fast-Moving Tropical Cyclone

Abstract The ocean temperature response to tropical cyclones (TCs) is important for TC development, local air–sea interactions, and the global air–sea heat budget and transport. The modulation of the upper ocean vertical temperature structure after a fast-moving TC was studied at the observation stations in the northern South China Sea, including TCs Kalmaegi (2014), Rammasun (2014), Sarika (2016), and Haima (2016). The upper ocean temperature and heat response to the TCs mainly depended on the combined effect of mixing and vertical advection. Mixing cooled the sea surface and warmed the subsurface, while upwelling (downwelling) reduced (increased) the subsurface warm anomaly and cooled (warmed) the deeper ocean. An ideal parameterization that depends on only the nondimensional mixing depth (HE), nondimensional transition layer thickness (HT), and nondimensional upwelling depth (HU) was able to roughly reproduce sea surface temperature (SST) and upper ocean heat change. After TCs, the subsurface heat anomalies moved into the deeper ocean. The air–sea surface heat flux contributed little to the upper ocean temperature anomaly during the TC forcing stage and did not recover the surface ocean back to pre-TC conditions more than one and a half months after the TC. This work shows how upper ocean temperature and heat content varies by a TC, indicating that TC-induced mixing modulates the warm surface water into the subsurface, and TC-induced advection further modulates the warm water into the deeper ocean and influences the ocean heat budget. Significance Statement Tropical cyclones can cause a strong ocean response that modulates the upper ocean temperature structure and contributes to the local heat budget and transport. This manuscript shows how mixing and vertical advection modulate upper ocean temperature after four fast-moving tropical cyclones, and then gives a parameterization of how sea surface temperature and upper ocean heat change depend on the two mechanisms. The temperature anomalies can propagate into deeper ocean after the tropical cyclones, and sea surface heat flux is not important for upper ocean temperature response during a tropical cyclone. These results show how the upper ocean temperature responses to a tropical cyclone, and influences the local heat budget.

The air-water heat exchange and water vertical stability in the Xiangxi Bay of Three Gorges Reservoir

水库或湖泊的热分层结构是其动力与环境过程的重要研究方面,虽然很多学者针对水体分层结构和演变机理开展了大量研究,但水体通过水-气界面与大气进行热交换的过程,各气象因子的贡献机理等研究成果还很缺乏。本文基于三峡水库香溪河库湾2019年3月-2020年2月期间的水温、水位及气象等监测数据,针对水-气界面热交换过程如何影响水温垂向结构及表层水体湍流混合作用开展研究。结果表明,(1) 香溪河水体年内呈高温期分层、低温期混合的基本特征,高温期混合层深度小于8 m,低温期混合层深度超过30 m。(2) 太阳短波辐射是香溪河水体的主要热源,潜热通量和长波辐射是香溪河水体的主要冷源,感热通量贡献极小。(3) 香溪河平均风速较弱,约为1.6 m/s,主要通过增强潜热和感热通量的方式影响水体垂向稳定性结构特征,其机械扰动作用较弱。(4) 表层水体湍能通量在高温期较低(10^-7 m³/s³量级),此时水体处于分层状态,风应力大概率主导表层水体湍流发育; 低温期表层水体湍能通量较高(10^-6 m³/s³量级),此时潜热通量和长波辐射主导表层水体湍流发育。;The thermal stratification structure of a reservoir or a lake is important to its dynamics and environmental process. Although many scholars have studied this topic, a gap is still existed on the process of heat exchange in the air-water interface and the contribution mechanism of various meteorological factors. In this paper, based on the observation data of water temperature and meteorology from March 2019 to February 2020, in Xiangxi Bay of the Three Gorges Reservoir, we studied how the heat flux and wind stress affect the vertical structure of water temperature and the turbulent mixing. We have conclusions as following. (1) The Xiangxi River is characterized as stratification in high temperature period and mixing in low temperature period. The depth of mixing layers in high temperature period is less than 8 m and that in low temperature period is more than 30 m. (2) Solar short-wave radiation is the main heat source of Xiangxi Bay, while latent heat flux and long wave radiation are the main cold source. The contribution of sensible heat flux is quite small. (3) The wind speed in Xiangxi River region is weak, with an average value about 1.6 m/s, which influence the water vertical stability by enhancing latent heat and sensible heat flux strongly and mechanical disturbance effect weakly. (4) The turbulent energy flux of surface water is much lower in the high-temperature period (10^-7 m³/s³ in magnitude), at which time the wind stress dominates the development of turbulence. The turbulent energy flux is quite high during low-temperature period (10^-6 m³/s³ in magnitude), when the sensible heat flux and long wave radiation dominate the turbulence mixing.

Joint Active and Passive Microwave Thermometry of Ice Sheets

Measurement of ice-sheet thermal state via microwave remote sensing techniques has the potential to provide critically needed observations on englacial temperature at the local and continental scale. Better constraints of the vertical englacial temperature structure are needed to improve understanding of thermomechanical processes, ice rheology, and basal sliding, and to reduce uncertainty in interpretations of basal conditions such as material, roughness, and thermal state. We investigate the potential to combine active and passive microwave remote sensing techniques, namely ice-penetrating radar sounding and microwave radiometry, to enable more precise, accurate, and robust measurement of ice-sheet thermal state across widely varying thermal regimes. We simulate the effects of englacial temperature profiles on the attenuation and brightness temperature and explore the performance tradeoffs for joint radar-radiometer system architectures. Our analysis shows that active and passive microwave measurements have complementary sensitivities to englacial temperature as a function of depth, and that a ground-based joint radar-radiometer system can reduce the requirements and complexity demanded of each single instrument.

Observation of a mesoscale warm eddy impacts acoustic propagation in the slope of the South China Sea

Acoustic rays are modified while propagating through oceanic eddies. However, due to the lack of field synchronous observation, the impact of mesoscale eddy on the acoustic propagation is less clarified. To address the issue, an eddy-acoustic synchronous observation (EASO) field experiment for a mesoscale warm eddy was carried out in the slope of the South China Sea (SCS) in October, 2021. During the field experiment, a total of 105 conductivity-temperature-depth (CTD) stations, as well as a zonal acoustic survey line through the center of the warm eddy, were obtained. The vertical structures of temperature and salinity indicate that the warm eddy is surface-intensified with temperature and salinity cores confined within depths from 70 m to 200 m and 10 m to 70 m, respectively. The acoustic observation shows two obvious convergency zones (CZs) at about 39 km and 92 km in the eastern half acoustic line, and one convergency zones (CZ) at about 25 km in the western half acoustic line. By comparing with the none eddy circumstance, the respective impacts of the topography and warm eddy are quantitatively analyzed with a ray-tracing model. The results indicate that the topography shortens the horizontal span of the CZ by 11.4 km, while the warm eddy lengthens it by 1.7 km. Additionally, the warm eddy shallows the depth and broadens the width of the CZ by 32 m and 1.4 km, respectively. The anisotropy of 3D sound fields jointly influenced by the warm eddy and the local topography show that the distance differences of the first CZs in different horizontal directions can be as long as 31 km.

Seasonal Changes in the Vertical Structure of Ozone in the Martian Lower Atmosphere and Its Relationship to Water Vapor

AbstractThe mid‐infrared channel of the Atmospheric Chemistry Suite (ACS MIR) onboard the ExoMars Trace Gas Orbiter is capable of observing the infrared absorption of ozone (O3) in the atmosphere of Mars. During solar occulations, the 003←000 band (3,000‐3,060 cm−1) is observed with spectral sampling of ∼0.045 cm−1. Around the equinoxes in both hemispheres and over the southern winters, we regularly observe around 200–500 ppbv of O3 below 30 km. The warm southern summers, near perihelion, produce enough atmospheric moisture that O3 is not detectable at all, and observations are rare even at high northern latitudes. During the northern summers, water vapor is restricted to below 10 km, and an O3 layer (100–300 ppbv) is visible between 20 and 30 km. At this same time, the aphelion cloud belt forms, condensing water vapor and allowing O3 to build up between 30 and 40 km. A comparison to vertical profiles of water vapor and temperature in each season reveals that water vapor abundance is controlled by atmospheric temperature, and H2O and O3 are anti‐correlated as expected. When the atmosphere cools, over time or over altitude, water vapor condenses (observed as a reduction in its mixing ratio) and the production of odd hydrogen species is reduced, which allows O3 to build up. Conversely, warmer temperatures lead to water vapor enhancements and ozone loss. The LMD Mars Global Climate Model is able to reproduce vertical structure and seasonal changes of temperature, H2O, and O3 that we observe. However, the observed O3 abundance is larger by factors between 2 and 6, indicating important differences in the rate of odd‐hydrogen photochemistry.

Vertical multiple-layer structure of temperature and turbulent diffusivity in the South China Sea

Vertical multiple-layer structure of temperature and turbulent diffusivity in the South China Sea

Vertical thermal environment of subtropical broad-leaved urban forests and the influence of canopy structure

Urban forests alter the surface energy balance and provide a comfortable thermal environment. However, little quantitative research exists on the relationship between their vertical temperature structure and influence on the urban thermal environment. In this study, we aimed to measure the differences and determine the correlations between the canopy temperature (T1), below-canopy air temperature (T2), below-canopy ground surface temperature (T3), and soil temperature (T4) of three forests: evergreen broad-leaved forest (EBF), deciduous broad-leaved forest (DBF), and mixed evergreen and deciduous broad-leaved forest (MBF) in Zhejiang Province, China. The thermal environment of DBF fluctuated greatly, whereas that of EBF and MBF was relatively stable. T1 was highly and significantly correlated with T2 (r > 0.850, p < 0.01) and T3 (r > 0.790, p < 0.01) in EBF and MBF; thus, T1 is a good predictor of T2 and T3 in EBF and MBF. T4 was susceptible to the external thermal environment and correlated relatively well with T2 (r = 0.879) in DBF. MBF and EBF had substantial cooling effects, with mean values of T2 and T3 2.4 and 2.3 °C, and 10.1 °C and 10.7 °C lower than the air and surface temperatures in the areas without canopy shade, respectively. Ambient temperature and humidity, solar radiation, canopy thickness and density, tree number, and tree species and height significantly influenced the thermal environment and cooling effect of the forests. The results of this study provide an important reference for the future design of thermally comfortable urban landscapes.

Characterizing vertical upper ocean temperature structures in the European Arctic through unsupervised machine learning

In-situ observations of subsurface ocean temperatures are, in many regions, inconsistently distributed in time and space. These spatio-temporal inconsistencies in the observational network lead to difficulties in utilizing those observations effectively for ocean model evaluation or understanding larger-scale ocean characteristics. Model accuracy of subsurface ocean characteristics is especially important within regions that contain complex ocean structures. One such region is the European Arctic which not only contains several types of water masses with unique characteristics, but also wintertime sea ice coverage and complex bathymetry. This study presents an unsupervised neural networking technique that can be used in combination with traditional ocean model evaluation techniques to provide additional information on the accuracy of modeled vertical ocean temperature profiles. Self-organizing maps is an unsupervised machine learning technique that we apply to approximately twenty thousand Argo and CTD temperature profiles from 2012 to 2020 in the European Arctic to categorize the observed vertical ocean temperature structures in the top 150 m. The observed ocean profile categories, or neurons, defined by the self-organizing map show strong spatial and temporal dependencies. We then use the neuron weights, or the learned temperature profile structure of each neuron, to validate the spatial and temporal variability of modeled vertical temperature structures. This analysis gives us new insights about the model’s capabilities to reproduce specific vertical structures of the top-most ocean layer within different regions and seasons. Mapping modeled ocean temperature profiles onto the neuron-space of the observationally-defined self organized map highlights the potential of this method to advance our understanding of model deficiencies in that region.

Extension and Evaluation of University of Washington Moist Turbulence Scheme to Gray‐Zone Scales

AbstractWith the rapid improvement in computational resources, it has become possible to structure numerical weather model simulations to use sub‐kilometer grid spacing. Traditional turbulence‐mixing closures have become obsolete within the context of the gray zone of turbulence. Here, a new scale‐aware algorithm (SA‐UW) is developed based on the UW (University of Washington Moist Turbulence) scheme. By dividing both the local and nonlocal vertical turbulence flux into sub‐grid and resolved parts, the partition of sub‐grid turbulence is tuned by a set of well‐acknowledged scale‐dependent relationships. Idealized simulations confirm that the newly developed scheme can adequately reproduce sub‐grid turbulence transport at gray‐zone scales. The inclusion of a nonlocal transport term in the SA‐UW scheme is essential, as it vastly improves the distribution and intensity of coherent structures. The SA‐UW scheme recovers the conventional UW scheme when grid spacing is larger than the turbulence length scale, thereby evincing the sale‐aware capability of the new method. For real‐case simulations, the SA‐UW scheme can capture the diurnal cycle and provide a more accurate vertical structure of temperature and humidity.

Characterizing a Heavy Dust Storm Event in 2021: Transport, Optical Properties and Impact, Using Multi-Sensor Data Observed in Jinan, China

On 15 March 2021, the strongest sandstorm of the last 10 years occurred in China. The MODIS, MPL lidar, EDM 180, ADI 2080 and Meteorological observation instruments were used to observe the dust in Jinan, China, while the HYSPLIT model was also employed to find the source. It was found that the dust originated from Mongolia and the Gobi desert and was transported to Jinan at night on 14th March, lasting until the 18th. Multi-layer dust was observed, of which the dust below the height of 1 km was strongest with the VDR about 0.2 and the maximum extinction coefficient up to 3 km−1. The values of AOD and AE were greater than 2 and less than 0.25, respectively. The mass concentrations of PM10 and PM2.5 increased rapidly, and were up to 573 µg/m3 and 3406 µg/m3, respectively. Additionally, the mass concentration ratio decreased rapidly, with a minimum of 17%. The particle size of the dust was mainly distributed between 0.58–6.50 micros due to larger particles increasing dramatically; simultaneously, both the proportion and the value for calcium ions in PM2.5 went up. The dust had an obvious impact on the vertical structure of the air temperature, resulting in occurrence of a strong inversion layer.

Representativeness and certainty of sea surface temperature from MODIS in semi-enclosed bays

ABSTRACT The sea surface temperature estimated by satellites (SSTskin) may facilitate the understanding of processes that affect water quality in semi-enclosed bays. However, the representativeness and certainty of SSTskin in semi-enclosed bays have not been fully investigated. We investigated the SSTskin from MODIS in Tokyo Bay and Ise Bay to test the hypothesis that water-mass structure and proximity to land would affect SSTskin. Results showed that the SSTskin from MODIS in two semi-enclosed bays can be as representative and certain as the data from previous studies in the open ocean. We found that horizontal gradients of water temperature had little effect on the certainty of SSTskin. However, we found that both the representativeness and certainty of satellite-based estimates of SSTskin in semi-enclosed bays were reduced by seasonal and location characteristics. The representativeness and certainty of SSTskin near the mouth of Ise Bay were compromised by the complex vertical structure of water temperature in summer. Because SSTskin may greatly enhance understanding of the processes that affect water quality in semi-enclosed bays, our results indicate that prior validation of SSTskin by comparison with in-situ sea surface temperature (SSTdep) is important.

Interactions between the North Brazilian Undercurrent (NBUC) and the Southwest Atlantic Margin. Implications for Brazilian shelf-edge systems

Western boundary currents influence the global ocean circulation and climate, whereas it locally reaches out differently to the continental margins. This study investigates the response of the North Brazilian Undercurrent (NBUC) over their interactions with the eastern and northern margins of the northeastern Brazil. The data set comprises regional bathymetry, in situ current measurements, CTD profiling, and simulations of oceanic currents using a regional model (CROCO). The physical analysis focuses on the months of February (austral summer) and August (austral winter). Horizontal and vertical structure of current velocity, temperature and salinity were correlated using maps and bathymetric profiles along the critical pathways of the NBUC. The eastern and northern margins are narrow and retracted with widths up to 40 km and steep upper continental slopes (14°). These margins are separated by the Touros High, which extends eastward up to 80 km offshore, with a shallow shelf (most parts are < 10 m) of approximately 55 km wide. The vertical sections of velocity show the NBUC shifting onto the Touros shelf in August and show that the strong trade winds during the austral winter handle the alongshore current circulation of this region. In the northern margin, the recirculation of the NBUC disturbs the base of the thermocline and part of these current fluxes toward the outer shelf region. The different patterns of the NBUC affect the sedimentary and ecological characteristics of eastern, Touros and northern outer shelves. Besides, the slope and outer shelf morphology might contribute to events of current-driven nutrient-enrichment and mixing processes at the base of the mixed layer. These results support the evidences that the western boundary current interactions by eddies and jets with the margin control the morpho-sedimentary and environmental conditions of the Brazilian outer shelf ecological system corridor.

Atmospheric Exploration of the Qinghai–Tibet Plateau during the East Asian Winter Monsoon (EAWM) from a Ground-Based Microwave Radiometer

The investigation of atmospheric characteristics is of great significance in properly exploiting air and water resources, and quantitatively estimating and nowcasting precipitation. Microwave radiometers are widely used in this field because they can operate unattended for a long time under almost all weather conditions, and obtain high-quality remote sensing data. This research focuses on the applications of ground-based microwave radiometers in retrieving meteorological characteristics of the Qinghai–Tibet Plateau (QTP) during the East Asian winter monsoon (EAWM), such as humidity and temperature structures, stability/convection indices, and cloud and precipitation retrievals. Vertical structures of atmospheric temperature, pressure, humidity, and other variables were investigated under clear-sky and snowy-sky conditions. The statistical characteristics of stability/convection indices in the QTP region, such as convective available potential energy (CAPE) and convective inhibition (CIN), were investigated, with a special focus on snowy-sky conditions. The relationship between potential cloud water resources and atmospheric and thermodynamics and instability conditions were taken into consideration. The results showed that the peak CAPEs under clear-sky and snowy-sky conditions were 1349.11 J/kg and 1165.12 J/kg, which were relatively larger than the corresponding values during the summer monsoon. CINs during the EAWM were small enough to be negligible. For quantitative precipitation forecasting (QPF), brightness temperatures at 30.0 GHz and 51.24 GHz sampling channels were sensitive to the snowfall process. Within 1 h before snowfall, the precipitable water vapour (PWV) and liquid water content (LWC) increased sharply by 0.05 cm and 0.12 mm, respectively, while the CAPE and downwards CAPE decreased by 225.60 J/kg and 180.31 J/kg, respectively. The findings of this article may be meaningful for characterizing meteorology and precipitation in the QTP and similar regions during the winter monsoon.

Evaluating the Eastward Propagation of the MJO in CMIP5 and CMIP6 Models Based on a Variety of Diagnostics

Abstract Given the climatic importance of the Madden–Julian oscillation (MJO), this study evaluates the capability of CMIP6 models in simulating MJO eastward propagation in comparison with their CMIP5 counterparts. To understand the representation of MJO simulation in models, a set of diagnostics with respect to MJO-associated dynamic and thermodynamic structures is applied, including large-scale zonal circulation, vertical structures of diabatic heating and equivalent potential temperature, moisture convergence at the planetary boundary layer (PBL), and the east–west asymmetry of moisture tendency relative to the MJO convection. The simulated propagation of the MJO in CMIP6 models shows an overall improvement in realistic speed and longer distance, which displays a robust linear regression relationship against the above-mentioned dynamic and thermodynamic structures. The improved MJO propagation in CMIP6 largely benefits from better representation of premoistening processes that is primarily contributed by improved PBL moisture convergence. In addition, the convergence of moisture and meridional advection of moisture prior to the MJO convection are enhanced in CMIP6, while the zonal advection of moisture is as weak as that in CMIP5. The increased convergence of moisture is a result of enhanced lower-tropospheric moisture and divergence, and the enhanced meridional advection of moisture can be caused by sharpened meridional gradient of mean lower-tropospheric moisture in the western Pacific. Further examination of the lower-tropospheric moisture budget reveals that the enhanced zonal asymmetry of the moisture tendency in CMIP6 is driven by the drying process to the west of the MJO convection, which is attributed to the negative vertical and zonal advections of moisture.