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Abstract Fishes commonly exhibit diel rhythms in movements with consequences to feeding, reproduction, predator evasion, and resting. Such behaviors are conceived as plastic, persisting for phases (days to weeks), and then becoming disrupted, masked, and altered by changed environmental or ecological conditions. In telemetered black sea bass Centropristis striata (family Serranidae), we documented a remarkable 4‐month record of persistent diurnal vertical movements. Within the U.S. Mid‐Atlantic Bight June–October 2019 setting, biotelemetry data of 31 fish were examined through time series analysis and generalized additive modeling. Sun altitude played a dominant role throughout the series, where movements were diurnal. Thermal conditions were uniform until a September hurricane caused a 10°C rise in inhabited waters within the span of six hours, the result of water column mixing. This and other storms caused short‐term disruptions (

Fishes commonly exhibit diel rhythms in movements with consequences to feeding, reproduction, predator evasion, and resting. Such behaviors are conceived as plastic, persisting for phases (days to weeks), and then becoming disrupted, masked, and altered by changed environmental or ecological conditions. In telemetered black sea bass Centropristis striata (family Serranidae), we documented a remarkable 4‐month record of persistent diurnal vertical movements. Within the U.S. Mid‐Atlantic Bight June–October 2019 setting, biotelemetry data of 31 fish were examined through time series analysis and generalized additive modeling. Sun altitude played a dominant role throughout the series, where movements were diurnal. Thermal conditions were uniform until a September hurricane caused a 10°C rise in inhabited waters within the span of six hours, the result of water column mixing. This and other storms caused short‐term disruptions (<2 d) to diel rhythmicity. Daytime vessel traffic, but not dolphin presence, caused ≤1 h refuge‐seeking excursions. The discovery of pelagic behaviors (up to 15 m off the seabed) requires revision to the species' natural history, which was previously conceived as exclusively demersal. Spring‐autumn movement functions included reef recruitment and evacuation, courtship and spawning, and seasonal changes in feeding ecology and predator fields. Throughout these phases, the cycle of daytime movement and nighttime inactivity persisted. We hypothesize that during the nocturnal period these visual specialists become immobile and thus evade predation and mobilize energy toward growth, reproduction, and storage. Because this function does not change from spring through autumn, we speculate that nocturnal quiescence serves as the proximate control for the diurnal activity cycle. [ABSTRACT FROM AUTHOR]

A squall line event that occurred in the south of the Yangtze River in China on 4 May 2020 was simulated using the WRF model and 3DVAR data assimilation. The radar radial wind, reflectivity, and conventional observation data were assimilated in a cycling interval of 15 min. The main findings from the examination of the development mechanisms of the squall line are as follows. The simulation effectively reproduced the development and evolution of the squall line. The squall line strengthened from the Wuling Mountains to the Dongting Lake Plain, moved eastwards and developed to its strongest stage over the plains, before weakening from thereon to the Mulianjiu Mountains. When the squall line moved from the mountains to the plains, the convergence of the airflow in front of the squall line increased because of the strengthening of the near-surface easterly airflow over the plains. Concurrently, the intensity of the cold pool behind the squall line decreased, while the low-level vertical wind shear over the plains increased. This reduced the gap between the cold pool and vertical wind shear. The low-level upward airflow in front of the cold pool tended to be vertical, which was conducive to the development and maintenance of the squall line. When the squall line moved eastwards from the plains to the mountains, the convergence of the airflow in front of the squall line weakened because of the weakening of the surface easterly airflow over the mountains. Concurrently, the intensity of the cold pool behind the squall line increased, while the low-level vertical wind shear in front of the squall line significantly declined. The intensity of the cold pool significantly exceeded the low-level vertical wind shear, inducing a tendency for the low-level upward airflow in front of the cold pool to tilt towards the cold pool, which was not conducive to the development and maintenance of the squall line. This was a reason why the squall line moved eastwards faster after going up the mountains. Based on these observational and simulation results, physical conceptual models for the enhancement of squall lines from the mountains to the plains and their weakening from the plains to the mountains have been preliminarily developed. • The differences in mesosclae features (cold pool, vertical shear) could explain the evolution of the squall line. • The strong wind and vertical shear over the plains are conductive to strengthening of the mountain-to-plain squall line. • The weak vertical wind shear over the mountains could be a key reason of weakening of the plain-to-mountain squall line. [ABSTRACT FROM AUTHOR]

On June 15, 2021, the Hotan region of southern Xinjiang was hit by an extreme rainfall event. A numerical simulation of the storm process, with a resolution of 3 km, was conducted to analyze the initiation mechanism of the rainfall. The results show that lifting conditions play a crucial role in triggering convection, compared to moisture and stratification conditions. The easterly jet changes the direction in the western part of the Tarim Basin and speeds up, creating a zone of high wind speeds in front of Kunlun Mountain's northern slope, which provides favorable conditions for convection initiation. A remarkable feature during this process is the effect of a preexisting distant cold pool on the southern slope of Tianshan Mountain. The cold pool impedes the easterly development of the easterly airflow in the basin, causing it to turn northward, and accelerates the mountain front airflow in front of Kunlun Mountain. The inner dynamic mechanism is a strengthening of the low-level horizontal pressure gradient between the cold pool and the low-pressure belt along Kunlun Mountain. The numerical sensitivity experiments also highlight the key role the distant cold pool plays in the development of the high-speed wind belt ahead of the mountain and causes convection to start 4 h earlier. These results will serve as a valuable reference for future studies on the formation process of convection and improve the understanding of precipitation forecast in arid and semi-arid regions. • The extreme rainfall in southern Xinjiang is affected by a preexisting distant cold pool. • The distant cold pool functions like a topographical barrier and blocks airflow. • The existence of the cold pool makes the deep convection occur earlier. [ABSTRACT FROM AUTHOR]

Abstract The lowest winter‐maximum areal sea‐ice coverage on record (1980–2019) in the Bering Sea occurred in the winter of 2017/2018. Sea ice arrived late due to warm southerly winds in November. More typical northerly winds (albeit warm) in December and January advanced the ice, but strong, warm southerlies in February and March forced the ice to retreat. The cold pool (shelf region with bottom water < 2 °C) was the smallest on record, because of two related mechanisms: (1) lack of direct cooling in winter by melting sea ice and (2) weaker vertical stratification (no ice melt reduced the vertical salinity gradient) allowing surface heating to penetrate into the near bottom water during summer. February 2019 exhibited another outbreak of warm southerly winds forcing ice to retreat. The number of >31‐day outbreaks of southerly winds in winter has increased since 2016.

Combining multiple observational data and ERA5 time-by-time reanalysis data, combined with a limited area wind field analysis method, the process of controlling the next fast-developing bow-shaped squall line of Hainan Island's subtropical high on April 22, 2020 was analyzed. The results show that under the background of the weaker environmental wind shear in Hainan Island, the interaction of gust fronts, ground β-mesoscale convergence lines, and small-scale thunderstorms quickly developed into a highly organized bow-shaped squall line, and a strong cold pool near the ground. Drive the storm to deviate from the average guided airflow and move quickly to the southeast. The divergent wind field obtained by the decomposition of the wind field more intuitively reflects the diagnostic information of the weather system than the original wind field. The high-altitude divergent wind field more clearly shows the convective development and the dissipated early high-altitude divergence on the original wind field. The ground mesoscale convergence line reflects the characteristics of strong ground convergence at the bow-shaped echo bulge and rapid advancement of the cold pool. The next 1h precipitation will be on the warm and wet inflow side near the convergence line. [ABSTRACT FROM AUTHOR]

Background: The detection efficiency of ultrasonic transmitters is seasonally variable, requiring long-term studies to evaluate key environmental features that mask, alter speed, bend, or reflect transmissions. The US Southern Mid-Atlantic Bight shelf is characterized by a strong summer thermocline capping remnant winter water, known as the Cold Pool, and a well-mixed water column in other seasons. To investigate the effects of interactions between temperature stratification and storm-induced noise on transmission detectability, we conducted a year-long range test of 69-kHz acoustic transmitters in the bottom waters of the US Southern Mid-Atlantic Bight. We used generalized additive models and cross-validation to develop and evaluate a predictive model of detection efficiency and visualize variability in detection distance throughout the year of deployment. Results: The most-predictive model contained the effects of temperature stratification and ambient noise, predicting that stratification results in a 33% increase in detectability and 56% increase in detection distance. The model had an overall error rate of 17.1% and an 18.7% error at a distance of 800 m, predicting 17% detectability at median ambient noise when the water column was not stratified and > 50% when the difference between surface and bottom temperatures was greater than 4.2 °C. The distance at 50% detectability increased with the formation of the Cold Pool during spring, increasing by nearly 300 m over 3 days. All seasons were associated with storm-induced reductions in overall detectability and distance at 50% detectability. Conclusion: Thermal stratification within the Southern Mid-Atlantic Bight increases bottom water ultrasonic transmitter detection distance and reduces the impact of surface noise. This effect leads to a seasonal increase in detection distance from the late-spring through the summer. To our knowledge, this study is the first to report and quantify an increase in detection range as a result of temperature stratification, likely due to placing transmitters and receivers on the same side of a strong thermocline. [ABSTRACT FROM AUTHOR]

Four typical double-moment cloud microphysical schemes (Milbrandt, Morrison, NSSL and WDM6) in WRF (Weather Research and Forecasting) are used to investigate the impact of the different schemes on the simulation of a straight squall line evolving into a bow-shaped one in East China on 15 April 2016. Although simulations with Milbrandt, Morrison and WDM6 schemes can produce bow-shaped squall lines, only the WDM6 scheme can simulate the evolution process of the straight squall line to a bow-shaped one well. The simulation results with the NSSL scheme produce a broken straight squall line. The possible reason is that the range and intensity of cold pools and the rear inflows are different among the four schemes when the observed squall line evolves into a standard bow-shaped squall line. The mixing ratio and number concentration of rain water with the WDM6 scheme is largest in strong convective areas, and the cold pool and rear inflow are also strongest among the four schemes. Compared with the WDM6 scheme, the mixing ratio and number concentration of rain water are less with the Milbrandt and Morrison schemes. Also, the cold pool and rear inflow with the Milbrandt scheme are weaker than for the WDM6 scheme but stronger than those with the Morrison scheme. The rainwater mixing ratio is very low and no obvious cold pool and rear inflow exist with the NSSL scheme.

An isolated convection was unexpectedly initiated in the evening of 1 August 2019 around the Tianjin urban region (TUR), which happened at some distance from the shear line at lower level and the preexisting convection to the South, analyzed by using ERA5 reanalysis data and observations from surface weather stations, and a S-band radar. The results show that, 42 min before the initiation of the convection, the atmospheric thermodynamic conditions around TUR were favorable for the initiation of the isolated convection, although the southerly and vertical shear of the horizontal wind at the lower level was weak. A sea-breeze front approached the TUR and continued to move West, leading to the triggering of the isolated convection in the context of the urban humid heat island (UHHI) effect. Subsequently, the gust front, which was formed between the cold pool away from the TUR and the warm and humid air of the UHHI, moved northward, approached the convection, and collided with sea breeze front, resulting in five reflectivity centers of isolated convection being merged and the convection’s development. Finally, the isolated convection split into two convections that moved away from the TUR and disappeared at 20:36 Beijing Time. The isolated convection was initiated and developed by the interaction of the sea breeze front and gust front in the context of the UHHI effect. The sea breeze front triggered the isolated convection around TUR in the context of the UHHI effect, and the gust front produced by the early convective storms to the south played a vital role in the development of the isolated convection.

Sub-hourly heavy precipitation events (SHHPs) frequently underlie major meteorological hazards, but their comprehensive analysis is still lacking in Portugal. A 71-weather-station dataset for 2000–2020 is used in this article to (1) diagnose SHHPs corresponding to a 10-min precipitation event of at least 5.0 mm, (2) characterize their spatial-temporal distribution, and (3) identify their associated synoptic-scale conditions. Two synoptic types are associated with SHHPs: remote (RemL) and regional (RegL) low-pressure systems. RegL SHHPs display two marked maxima in spring and autumn, while RemL SHHPs show a single maximum in autumn. Most RegL events occur in the afternoon/evening, while RemL events show a slight bias toward midday occurrences. In the case of RemL, the wind is stronger for 2 to 3 h before and during SHHPs, veers from 180° to 210° near the event, the pressure decreases until 20 min before the event, and the wet-bulb temperature decreases around the time of the event and remains low, thus reflecting cold-front passages. For RegL, maximum winds coincide with precipitation peaks, and the wet-bulb temperature briefly decreases in association with downdrafts. A preliminary relationship between the SHHPs and mesoscale convective systems is established by detecting sudden surface-pressure surges, which are indicative of mesohighs caused by evaporatively cooled downdrafts. A calendar of mesohigh episodes linked to SHHPs is provided herein and their signatures are illustrated for the “Pedrógão-Grande” fires. Indicators of several downbursts, cold pools, and mesohighs were identified by the AROME forecast. This first, systematized analysis paves the way to identifying dynamic precursors, enabling their integration into early warning systems and climate projections.

Abstract Cold pools influence convective initiation and organization, dust lofting, and boundary layer properties, but little is known about their interactions with the land surface, particularly in dry continental environments. In this study, two‐way cold pool‐land surface interactions are investigated using high‐resolution idealized simulations of an isolated, transient cold pool evolving in a dry convective boundary layer. Results using a fully interactive land surface demonstrate that sensible heat fluxes are suppressed at the center of the cold pool but enhanced at the edge due to the spatial patterns of land surface cooling and the air temperature and wind speed perturbations. This leads to cold pool dissipation from the edge inward. Latent heat fluxes are primarily suppressed within the cold pool, and the magnitude of this suppression is controlled by competition between atmospheric and land surface effects. By comparing the fully interactive land surface simulation to a simulation with imposed surface fluxes, the land surface‐cold pool feedbacks are shown to reduce the cold pool lifetime, extent, and intensity by up to 50% and influence the pattern of boundary layer turbulent kinetic energy recovery, which have significant implications for cold pool‐induced convective initiation.

The impacts of different moisture profiles on the structure and vertical motion of squall lines were investigated by conducting a set of numerical simulations. The base state was determined by an observational sounding, with high precipitable water representing moist environmental conditions in the East Asian monsoon region. To reveal the impact of moisture at different levels, the moisture content at the middle and low levels were changed in the numerical simulations. The numerical results showed that more convective cells developed and covered a larger area in the high moisture experiments, which was characteristic of the convection during the Meiyu season in China. In addition, high moisture content at low levels favored the development of updrafts and triggered convection of greater intensity. This was demonstrated by the thermodynamic parameters, including Convective Available Potential Energy (CAPE), Lifted Index (LI), Lift Condensation Level (LCL), and Level of Free Convection (LFC). Dry air at middle levels led to strong downdrafts in the environment and updrafts in clouds. This could be because dry air at middle levels favors the release of latent heat, thereby promoting updrafts in clouds and downdrafts in the environment. Therefore, high relative humidity (RH) at low levels and low RH at middle levels favors updrafts in the cloud cores. Additionally, moist air at low levels and dry air at middle levels promotes the development of convective cells and the intensification of cold pool. The squall line can be organized by the outflow boundary induced by cold pool. The balance of cold pool and environmental wind shear is favorable for the maintenance and strengthening of squall lines. [ABSTRACT FROM AUTHOR]

The Mid‐Atlantic Bight (MAB) Cold Pool is a bottom‐trapped, cold (temperature below 10°C) and fresh (practical salinity below 34) water mass that is isolated from the surface by the seasonal thermocline and is located over the midshelf and outer shelf of the MAB. The interannual variability of the Cold Pool with regard to its persistence time, volume, temperature, and seasonal along‐shelf propagation is investigated based on a long‐term (1958–2007) high‐resolution regional model of the northwest Atlantic Ocean. A Cold Pool Index is defined and computed in order to quantify the strength of the Cold Pool on the interannual timescale. Anomalous strong, weak, and normal years are categorized and compared based on the Cold Pool Index. A detailed quantitative study of the volume‐averaged heat budget of the Cold Pool region (CPR) has been examined on the interannual timescale. Results suggest that the initial temperature and abnormal warming/cooling due to advection are the primary drivers in the interannual variability of the near‐bottom CPR temperature anomaly during stratified seasons. The long persistence of temperature anomalies from winter to summer in the CPR also suggests a potential for seasonal predictability. Plain Language Summary: The interannual variability of the Mid‐Atlantic Bight (MAB) Cold Pool is investigated based on a long‐term (1958–2007) high‐resolution regional numerical model of the northwest Atlantic Ocean. The Cold Pool is a relatively cold and fresh water mass that exists below the surface and is located over the mid‐shelf and outer‐shelf of MAB. A Cold Pool Index (CPI) is defined and computed based on its persistence time, volume, temperature, and seasonal along‐shelf propagation and is used to quantify the strength of the Cold Pool in different years. The Cold Pool years are then categorized as strong, weak, and normal years based on the CPI. A detailed quantitative heat budget study of the Cold Pool region (CPR) has been examined in order to expose the main drivers of the interannual variability. Results suggest that the initial winter‐time temperature and warming/cooling due to advection are the primary drivers in controlling the interannual variability of the near‐bottom CPR temperature during spring and summer. The long persistence of temperature anomalies from winter to summer in the CPR also suggests a potential for seasonal predictability of the Cold Pool. Key Points: The Cold Pool interannual variability regarding its persistence, volume, temperature, and propagation is investigated using a multidecadal numerical modelA Cold Pool strength index is defined and used to identify extreme yearsInterannual variability of the near‐bottom Cold Pool temperature is controlled by initial winter temperature and total oceanic advection [ABSTRACT FROM AUTHOR]

Evolution characteristics of a squall line process occurred in Guangxi Province on 4 March 2018 were analyzed with NCEP-FNL data, Doppler radar data, wind profiler data and the intensive surface AWS data. The results showed that the squall line occurred when the thunderstorm cells entered Guangxi Province and organized into a linear convection in appropriate environmental condition. Consolidation of thunderstorm cells caused by strong southwest air current in the middle and lower troposphere, and forced lift of thunderstorm outflow boundary, were the direct causes of the squall line. Guangxi Province was in a strong low-altitude vertical wind shear environment before and during the occurrence of the squall line, there was a relatively high-low-high distribution in northern Guangxi from west to east, and wind shear vector was nearly perpendicular to the squall line. Variation of the ratio of propagation velocity of cold pool to vertical wind shear could well correspond to the evolution characteristics of squall line. The dissipation of the squall line could be better explained if we correct the ratio by incorporating the wind shear caused by the jet at rear of the squall line into the low-level wind shear. [ABSTRACT FROM AUTHOR]

On 14 June 2015, a severe afternoon thunderstorm event developed within the Taipei Basin, which produced intense rainfall (with a rainfall rate of 131 mm h-1) and urban-scale flooding. Cloud-resolving simulations using the Weather Research and Forecasting (WRF) model were performed to capture reasonably well the onset of the sea breeze and the development and evolution of this afternoon thunderstorm system. The WRF model had four nested grids (with the finest grid size of 0.5 km) in the horizontal direction and 55 layers in the vertical direction to explicitly resolve the deep convection over complex terrain. It was found that convection was initiated both by the sea breeze at foothill and by the upslope wind at the mountain peak. Convective available potential energy (CAPE) was increased from 800 to 3200 J kg-1 with abundant moisture transport by the sea breeze from 08 to 12 LST, fueling large thermodynamic instability for the development of the afternoon thunderstorm. Strong convergence between the sea breeze and cold-air outflow triggered further development of intense convection, resulting in heavy rainfall over Taipei City. Microphysics sensitivity experiments showed that evaporative cooling played a major role in the propagation of cold-air outflow and the production of heavy rainfall within the basin plain (terrain height < 100 m), whereas melting cooling played a minor role. The terrain-removal experiment indicated that the local topography of Mount Datun at the coastal region may produce the channel effect through the Danshui River Valley, intensify sea-breeze circulation, and transport more moisture. This terrain-induced modification of sea breeze circulation made its dynamic and thermodynamic characteristics more favorable for convection development, resulting in a stronger afternoon thunderstorm system with heavy rainfall within Taipei City. [ABSTRACT FROM AUTHOR]

Convection initiation (CI) associated with a cold pool gust front (GF) of a mesoscale convective system (MCS) occurred in the Bohai Bay region, North China, is investigated using a real‐data, high‐resolution Weather Research and Forecasting model (WRF) simulation. Observations revealed that many CIs occurred successively near the GF, most of which developed significantly in both size and intensity and eventually merged with the MCS. The WRF simulation captured the general features of the CIs, GF, and MCS. Lagrangian vertical momentum budgets were conducted along the backward trajectories of air parcels within a convective cell initiated near the GF. The total vertical acceleration was decomposed into dynamic and buoyant components. The results showed that the dynamic acceleration played a decisive role for the CI, which can be further decomposed into five terms. The horizontal curvature term was rather small, with the height variation of air density almost zero. Although both vertical and horizontal extension terms played a positive role during the CI process, the vertical twisting term had the greatest contribution to the CI. This reflects the vertical tilting (to the forward of the GF) of an elevated updraft which was generated by the convergence of a forward‐tilting updraft at the GF leading edge and another airflow coming from ahead of the GF. Key Points: Dynamic acceleration plays a decisive role for the convection initiation associated with a cold pool gust front (GF) in Bohai Bay regionVertical twisting related to horizontal vorticity has the greatest contribution to the dynamic accelerationForward‐tilting updraft above the GF and another airflow from ahead of the GF are converged and vertically tilted to form vertical twisting [ABSTRACT FROM AUTHOR]

An extreme rainfall event occurred in northern China between 18 and 21 July 2016, with the strongest precipitation of 783.4 mm occurring within the rainfall zone of Taihang Mountain. In this study, mesoscale convective systems (MCSs) resulting in heavy rainfall are studied using high-resolution surface observations, soundings and radar data. The topographic effect in addition to shear zone cyclonic circulation is mainly responsible for the heavy rainfall. The synoptic low-pressure environmental circulation promotes mesocyclone and convection development in northern China, where a strong and moist low-level jet is observed. The interaction between the mesocyclone and mesoscale topography produces two strong, separate precipitation centers, which are clearly the direct results of three MCSs. Orographic blocking plays a crucial role in the development of MCSs. Diabatic cooling due to raindrop evaporation in association with MCS1 forms a cold pool on the plain east of the central Taihang Mountain area. Convective cell initiation and development in MCS2 is due to the impingement of southeasterly flow near the surface of the hills east of Linzhou basin. Convective cells that are successively generated and shifted along a mesoscale shear line comprise the MCS2 linear distribution and a northwestward rain belt. The northern extreme rainfall center is caused by MCS3 along the southern slopes of an eastward-opening valley. Convective cells are triggered along a shear line, which is affected by a combination of topography, a cold pool in the boundary layer and mesocyclone outer flow. Together, the orographic forcing and cold pool enhance the Taihang Mountain precipitation event. • This article highlights the effect of the mesoscale topography on an extreme rainfall event. A synthetic schema of the development of the MCSs, in addition to the interaction with the mesoscale topography, is shown in Fig. 16. • Convective cells in MCS3 are triggered along a shear line, which is affected by a combination of topography, a cold pool in the boundary layer and mesocyclone outer flow. Together, the orographic forcing and cold pool enhance the Taihang Mountain precipitation event. The fact is rarely found in previous studies on precipitation in Taihang Mountain. [ABSTRACT FROM AUTHOR]

Background: Studies that attempt to measure shifts in species distributions often consider a single species in isolation. However, understanding changes in spatial overlap between predators and their prey might provide deeper insight into how species redistribution affects food web dynamics. Predator–prey overlap metrics: Here, we review a suite of 10 metrics [range overlap, area overlap, the local index of collocation (Pianka's O), Hurlbert's index, biomass‐weighted overlap, asymmetrical alpha, Schoener's D, Bhattacharyya's coefficient, the global index of collocation and the AB ratio] that describe how two species overlap in space, using concepts such as binary co‐occurrence, encounter rates, spatial niche similarity, spatial independence, geographical similarity and trophic transfer. We describe the specific ecological insights that can be gained using each overlap metric, in order to determine which is most appropriate for describing spatial predator–prey interactions for different applications. Simulation and case study: We use simulated predator and prey distributions to demonstrate how the 10 metrics respond to variation in three types of predator–prey interactions: changing spatial overlap between predator and prey, changing predator population size and changing patterns of predator aggregation in response to prey density. We also apply these overlap metrics to a case study of a predatory fish (arrowtooth flounder, Atheresthes stomias) and its prey (juvenile walleye pollock, Gadus chalcogrammus) in the Eastern Bering Sea, AK, USA. We show how the metrics can be applied to understand spatial and temporal variation in the overlap of species distributions in this rapidly changing Arctic ecosystem. Conclusions: Using both simulated and empirical data, we provide a roadmap for ecologists and other practitioners to select overlap metrics to describe particular aspects of spatial predator–prey interactions. We outline a range of research and management applications for which each metric may be suited. [ABSTRACT FROM AUTHOR]

A squall line that occurred in south China on 31 March 2014 was simulated with the Weather Research and Forecasting model. The microphysical processes had an important influence on the dynamic and thermodynamic structure of the squall line. The process of water vapor condensation (PCC+) provided heat for the ascending movement inside the squall line. The forward movement of the heating area of PCC+ was an important reason for the squall line’s tilting. The convergence of the outflow of the cold pool and the warm and wet air constantly triggered new convection cells in the front of the cold pool, which made the squall line propagate forwards. The cooling process of graupel melting into rain corresponded closely with the rear inflow jet. During the mature period of the squall line, the effect of cooling strengthened the rear inflow jet. This promoted low-layer inflow and a convective ascending motion, thus further promoting the development of the squall line system. During the decay period, the strong backflow center of the stratospheric region cut off the forward inflow of the middle and low layer towards the high layer, and cooperated with the cold pool to cut off the warm and wet air transport of the low layer, making the system decline gradually.

In an overall approach aiming at the development and qualification of various tools designed to diagnose and/or forecast the flows at the local scale in complex terrain, we qualified a numerical model based on the WRF platform and operated in a two-way nested domain mode, down to a horizontal resolution of 111 m for the smallest domain. The area in question is the Cadarache valley (CV), in southeast France, which is surrounded by hills and valleys of various sizes. The CV dimensions (1 km wide and 100 m deep) favor the development of local flows greatly influenced by the diurnal cycle and are prone to thermal stratification, especially during stable conditions. This cycle was well documented due to permanent observations and dedicated field campaigns. These observations were used to evaluate the performance of the model on a specific day among the intensive observation periods carried out during the KASCADE-2017 campaign. The model reproduced the wind flow and its diurnal cycle well, notably at the local CV scale, which constitutes considerable progress with respect to the performances of previous WRF simulations conducted in this area with kilometric resolution, be it operational weather forecasts or dedicated studies conducted on specific days. The diurnal temperature range is underestimated however, together with the stratification intensity of the cold pool observed at night. Consequently, the slope drainage flows along the CV sidewalls are higher in the simulation than in the observations, and the resulting scalar fields (such as specific humidity) are less heterogeneous in the model than in the observations.

During the summer monsoon season, strong coastal upwelling occurs along the southwest coast of India and at the southern tip of India, which cools the surface temperature of the waters around these regions. The summer monsoon current carries the upwelled cold waters into the Bay of Bengal and forms the ‘cold pool of the Bay of Bengal’, with its core south of Sri Lanka and over the south-central Bay of Bengal. The present study focuses on the intrusion of these cold waters into the south of the Bay of Bengal, its interannual variability, and its association with the surface wind during the break phase of the summer monsoon, when strong westerly surface winds flow south of 10°N. The authors hypothesize that the enhanced cooling in the cold pool region during monsoon spells is associated with the strong westerly wind stress there during the break spells of the monsoon. Seven cases of long break monsoon spells that occurred during the nine years from 2001 to 2009 are analyzed, and the results confirm our hypothesis.

The lowest winter‐maximum areal sea‐ice coverage on record (1980–2019) in the Bering Sea occurred in the winter of 2017/2018. Sea ice arrived late due to warm southerly winds in November. More typical northerly winds (albeit warm) in December and January advanced the ice, but strong, warm southerlies in February and March forced the ice to retreat. The cold pool (shelf region with bottom water < 2 °C) was the smallest on record, because of two related mechanisms: (1) lack of direct cooling in winter by melting sea ice and (2) weaker vertical stratification (no ice melt reduced the vertical salinity gradient) allowing surface heating to penetrate into the near bottom water during summer. February 2019 exhibited another outbreak of warm southerly winds forcing ice to retreat. The number of >31‐day outbreaks of southerly winds in winter has increased since 2016. Key Points: Wind patterns have changed in the Bering Sea, with a marked increase in warm southerly winds since 2016These changes in winds have resulted in decrease in sea ice, with the lowest extent ever observed in the Bering Sea occurring in 2017/2018The low ice extent restructured the horizontal temperature patterns, resulting in an almost nonexistent cold pool in August 2018 [ABSTRACT FROM AUTHOR]

This study contrasts characteristics of mature squall‐line mesoscale convective systems (MCSs) observed by extended ground‐based radar wind profiler (RWP) deployments from the U.S. Department of Energy Atmospheric Radiation Measurement program. This analysis compares the dynamical structure, precipitation, and cold pool properties associated with MCS events over RWP sites in Oklahoma, USA, (midlatitude) to those observed during a 2‐year RWP deployment to Manaus, Brazil, during GoAmazon2014/5 campaign (tropical). The MCSs indicate similar convective line rainfall rates and total rainfall accumulations. However, midlatitude events suggest a larger fractional stratiform contribution to total precipitation. For both regions, convective line cold pools are associated with sharp decreases (approximately 10 K) in the surface equivalent potential temperature (θe) near the time of line passage. Surface θe properties for both regions suggest a modest relationship between rainfall rate and the probability of observing measurable surface rainfall. The probability of observing convective updrafts in both tropical and midlatitude MCS events is found to be similar as a function of low‐level radar reflectivity. However, midlatitude MCSs are associated with more intense convective updrafts, with upward air motions (mean, maximum) peaking at higher altitude. The most pronounced contrast is the propensity for deeper and more intense downdrafts in midlatitude MCSs. An analysis based on observed downdraft properties is performed using simple mixing assumptions. For these events, the vertical gradient of θe in the lower troposphere is relatively consistent between the Amazon and Oklahoma, suggesting similar mixing rates for downdrafts originating below 3 km (0.1 km−1). However, if downdrafts originate nearer to the level of minimum θe at SGP, mixing may be occurring at rates comparable to 0.3 km−1. Key Points: Mesoscale systems in Amazonia and Oklahoma have similar rain rates, cold pool properties, and inferred mixing rates for low‐level downdraftsMesoscale systems in Oklahoma show intense updrafts peaking at higher altitudes and greater stratiform rain fractions than Amazon systemsOklahoma systems produce strong downdrafts that occur more frequently at higher altitudes (up to 6 km with mixing) than Amazon systems [ABSTRACT FROM AUTHOR]

Tropical and extratropical storms commonly occur in the Northwest Atlantic Ocean, sometimes causing catastrophic losses to coastal fisheries. Still, their influence on fish movements and range shifts is poorly known. We coupled biotelemetry observations of black sea bass in the U.S. Mid-Atlantic Bight with numerical modelling of the coastal ocean to evaluate the influence of Hermine (3–8 September 2016) on cold pool thermal destratification and fish evacuation. Spring through fall, black sea bass is a sedentary species, with movements focused on structure where they support important commercial and recreational fisheries. During summer 2016, we characterized the movements of 45 acoustically tagged black sea bass at three sites deploying acoustic receivers moored in shelf waters 18–31 km east of Ocean City, Maryland, and at depths 20–32 m in the southern Mid-Atlantic Bight. On 3 September 2016, cyclonic winds of Hermine caused rapid destratification of the water column. At experimental sites, bottom temperatures rose from 13 to 23°C in 10 h. An oceanographic model and observing data showed that the effects of this destratification dominated large portions of the Mid-Atlantic Bight and had long term effects on seasonal evolution of the shelf temperature. Nearly half of remaining black sea bass on 3 September (40%) permanently evacuated the experimental sites. Those that remained showed long-term depressed activity levels. Although the cause of this incomplete evacuation is unknown, it exemplifies partial migration, which may buffer black sea bass to regional impacts of changed timing or increased incidence of tropical storms. [ABSTRACT FROM AUTHOR]

The climate regime in the eastern Bering Sea has recently been dominated by a pattern of multi-year stanzas, in which several successive years of minimal sea-ice formation and warm summer temperatures (e.g., 2002-2005, 2014-2017) alternate with several years of relatively extensive sea-ice formation and cold summer temperatures (e.g., 2006-2013). This emerging climate pattern may be forcing long-term changes in the spatial distributions of the Bering Sea's marine fauna. The National Marine Fisheries Service's Alaska Fisheries Science Center recently conducted two bottom trawl surveys covering the entire Bering Sea shelf from the Alaska Peninsula to the Bering Strait. The first, in the summer of 2010, was conducted during a cold year when the majority of the continental shelf was covered by a pool of cold (< 2 °C) water. The second, in the summer of 2017, was during a warmer year with water temperatures above the long-term survey mean. These two surveys recorded significantly different spatial distributions for populations of several commercially important fish species, including walleye pollock (Gadus chalcogrammus), Pacific cod (Gadus macrocephalus), and several flatfish species, as well as jellyfishes. Population shifts included latitudinal displacement as well as variable recruitment success. The large-scale distributional shifts reported here for high-biomass species raise questions about long-term ecosystem impacts, and highlight the need for continued monitoring. They also raise questions about our management strategies for these and other species in Alaska's large marine ecosystems. [ABSTRACT FROM AUTHOR]

The initiation of second‐generation convective storms by the cold pools of first‐generation storms is known to depend on cold pool characteristics such as depth and speed. It is not clear, however, how these characteristics relate back to the convective storm components and, in turn, to the environment. Here we investigate the hypothesis that wider updraft cores result in wider downdraft cores, which subsequently lead to the development of deeper cold pools that are more likely to initiate new convection. This hypothesis is addressed using a large set of idealized numerical simulations of highly organized convective storms, specifically, supercells. Quantifications of the convective components show strong interrelationships between updraft area, downdraft area, and cold pool depth, thus supporting our primary hypothesis. These interrelationships are highly sensitive to the parcel buoyancy and vertical wind shear, with large convective available potential energy, strong wind shear, and a deep mixed layer ultimately contributing to the deepest (and strongest) cold pools. Diagnoses of the forcings of vertical accelerations show that draft width, and therefore cold pool depth, are initially influenced by the buoyancy and linear dynamic forcings, but thereafter are controlled mostly by the nonlinear dynamic forcings. These results, overall, have implications on the development (or improvement) of cold pool parameterizations in weather and climate models. Key Points: Strong interrelationships are found between updraft width, downdraft width, and cold pool depthThese interrelationships are highly sensitive to the parcel buoyancy and vertical wind shearStrong vertical wind shear, large convective available potential energy, and deep mixed layer support widest drafts and deepest cold pools [ABSTRACT FROM AUTHOR]

Abstract Since 2009, we have deployed 167 satellite tags on loggerheads within the U.S. Mid-Atlantic Bight of the Northwest Atlantic Ocean. These tags collect and transmit location, temperature and depth information and have yielded 18,790 temperature-depth profiles during the highly stratified season (01 June –04 October) for the region. This includes 16,371 profiles exceeding the mixed-layer depth, and, of those, 11,591 full water column profiles reaching the ocean floor. The US MAB is a dynamic ecosystem that is difficult to model due to a combination of complex seasonal water masses and currents and a limited set of tools for taking in situ measurements. This region is also prime foraging habitat for loggerhead sea turtles during the late-spring to summer months. Here we suggest that the habitat usage of loggerhead turtles in the Mid-Atlantic Bight make them good ocean observers within this difficult to model, highly stratified region. The use of turtle-borne telemetry devices has the potential to improve resolution of in situ temperature through depth data and in turn improve oceanographic model outputs. It is imperative that model outputs are continuously updated, as they are regularly used to inform management and conservation decisions. Highlights • Data loggers on turtles collected 18,790 temperature-depth profiles. • Profiles were collected during the highly stratified season within the US MAB. • This is a replicable method to study the oceanography of mid-latitude shelf seas. [ABSTRACT FROM AUTHOR]

The Mid‐Atlantic Bight (MAB) Cold Pool is a distinctive cold (lower than 10 °C) and relatively fresh (lower than 34 practical salinity unit) water mass. It is located over the middle and outer shelf of the MAB, below the seasonal thermocline, and is attached to the bottom. Following this definition, we put forward a method that includes three criteria to capture and quantify Cold Pool characteristics, based on a 50‐year (1958–2007) high‐resolution regional ocean model hindcast. The seasonal climatology of the Cold Pool and its properties are investigated during its onset‐peak‐decline cycle. Three stages of the Cold Pool event are defined according to its evolution and characteristics. The Cold Pool cores travel along the 60‐m isobath starting south of the New England shelf to the Hudson Shelf Valley at a speed of 2–3 cm/s. Furthermore, the northern extent of the Cold Pool retreats about 2.6 times faster than the southern extent during the summer progression. The heat balance of near‐bottom waters over the MAB and Georges Bank is computed and it is found that the heat advection, rather than vertical diffusion, dominates the resulting spatial patterns of warming. Possible origins of the Cold Pool are investigated by performing a lead‐lag correlation analysis. Results suggest that the Cold Pool originates not only from local remnants of winter water near the Nantucket Shoals, but has an upstream source traveling in the spring time from the southwestern flank of the Georges Bank along the 80‐m isobath. Plain Language Summary: The Mid‐Atlantic Bight (MAB) Cold Pool is a bottom‐trapped relatively cold and fresh water mass over the middle and outer continental shelf. It is a seasonal thermal feature that emerges during spring and summer when the water column is warmer at the surface. We use three criteria to quantify the Cold Pool and investigate its seasonal evolution of properties. We find the Cold Pool typically experiences an onset‐peak‐decline cycle during a year. Its coldest part travels along the 60‐m isobath at a speed of 2–3 cm/s from the south of the Nantucket Shoals to the Hudson Shelf Valley. During its seasonal collapse, the northern and southern boundaries retreat at different speeds, with the northern boundary retreating 2.6 times faster. In order to investigate relative importance of vertical mixing and advection of heat, we build a heat balance of the water column below 30 m depth. Results suggest that vertical mixing is the main reason for the warming in the Cold Pool, however, horizontal and vertical advection of heat that regulates the spatial difference in warming rates of the Cold Pool. We further discuss the possible origins of the Cold Pool. Key Points: The Cold Pool travels equatorward along the 60‐m isobath at a speed of 2–3 cm/s with a warming rate of about one degree Celsius per monthThe northern extent of the Cold Pool retreats 2.6 times faster than the southern extentVertical and horizontal advection, rather than vertical diffusion, modulate the geographical differences in warming trends [ABSTRACT FROM AUTHOR]

In synoptic meteorology, establishment of cold air masses at the middle and upper levels of the atmosphere is called cold air cell or cold air pool (Cold Pool). In this study the role of the cold pool in developing or intensifying the precipitation was examined by studying the synoptic maps for the period from 2007 to 2013 and 118 cases were identified. Synoptic maps, thermodynamic diagram (SkewT) and the distribution of rainfall on the selected days were investigated over East Azerbaijan province. The results showed that cold pool appears in three different synoptic patterns, temperature trough, closed cell or combination of trough and cell (at different levels). Although cold pool has been observed in warm season but the highest frequency appears in May. Investigation of rainfall recorded at the meteorological stations showed that 64% rainfall and 12.2% intense rainfall that has caused flood had been occurred in the establishment of cold pool. The results of thermodynamic diagrams' information indicated that although in most cases of atmospheric instabilities is confirmed by the indicator but in some cases weaknesses was observed in defining air instability which shows that dynamic condition (compared to the thermodynamic) is dominant during the establishment of cold pool. Finally, whenever the temperature difference in 850 and 500 level gets higher the probability of occurrence of intense rainfall, hail and flood are increased.

Local strong sandstorms (LSSs) in northwestern China often occur suddenly in tens of minutes during the late afternoon and by dusk. Observations and theoretical studies have shown the trigger role of cold-air pools over desert areas for the occurrence of LSS. In this study, a numerical heat convection model was established to simulate an LSS that was induced by a single cold pool with vertical helicity to study the evolution process. The Reynolds averaged Navier−Stokes (RANS) method was used for the numerical calculation to illustrate different stages of the evolution process of an LSS. Results show that after the intrusion of a cold pool into the upper region of the surface convective mixing layer, descending of the cold air would lead to the downward transport of vorticity, enabling thermal convection cells in the mixing layer to become swirling convection cells. After LSS is fully developed, there occurs many subvortices (secondary vortices) in the convection field. The velocity at different altitudes over selected positions in the calculation domain is consistent with the "lobe" shape of an LSS. The secondary vortices cause quick and huge energy dissipation and the decay of the LSS. These results are consistent with observations and indicate the crucial effect of convection cells structure in the mixing layer and the cold pool in the upper layer on the formation of LSS.

On July 13, 2012, a bow echo was observed over the lee side of the Mt. Halla (1,950 m above sea level) on Jeju Island, Korea. Three-dimensional (3D) wind-field and surface observation analyses were carried out to understand the structure and evolution of convective systems with a bow echo on a bell-shaped terrain. A northeastward-moving convective system passed over the approximately bell-shaped isolated mountain with a mean speed of 17 m s-1. On the windward side of the mountain, the convective system developed by the inflow of unstable warm air from the ocean and terrain-induced upward motion, even with a low convective available potential energy value of 511 J kg-1. When passing the lee side of the mountain, a bow echo was formed in the convective system by the strongest winds behind the bow echo. Behind the leading edge of the bow echo, the strengthened rear-inflow jet descended with relatively dry air along the surface, resulting in enhancing evaporative cooling. The precipitation-induced downdrafts generated a cold pool on the lee side of the mountain. The development of an rear-inflow jet and cold pool formation both contributed to the evolution of the bow echo. In addition, the isolated bell-shaped terrain had a major indirect influence on the evolution of the convective system with a bow echo in this event. [ABSTRACT FROM AUTHOR]

Abstract: Cold pools influence convective initiation and organization, dust lofting, and boundary layer properties, but little is known about their interactions with the land surface, particularly in dry continental environments. In this study, two‐way cold pool‐land surface interactions are investigated using high‐resolution idealized simulations of an isolated, transient cold pool evolving in a dry convective boundary layer. Results using a fully interactive land surface demonstrate that sensible heat fluxes are suppressed at the center of the cold pool but enhanced at the edge due to the spatial patterns of land surface cooling and the air temperature and wind speed perturbations. This leads to cold pool dissipation from the edge inward. Latent heat fluxes are primarily suppressed within the cold pool, and the magnitude of this suppression is controlled by competition between atmospheric and land surface effects. By comparing the fully interactive land surface simulation to a simulation with imposed surface fluxes, the land surface‐cold pool feedbacks are shown to reduce the cold pool lifetime, extent, and intensity by up to 50% and influence the pattern of boundary layer turbulent kinetic energy recovery, which have significant implications for cold pool‐induced convective initiation. [ABSTRACT FROM AUTHOR]

Abstract: The observed increase of convective extreme precipitation intensities with temperature beyond the Clausius‐Clapeyron rate has recently directed attention to nonequilibrium processes that might cause the increase. While out‐of‐equilibrium simulations with perturbed heating conditions show clear increases in convective precipitation intensities, it has so far remained unclear, to which extent precipitation intensities can increase, when the atmosphere is in “perpetual equilibrium” (PE). We use the term PE to describe periodically forced diurnal cycles that eventually yield an approximately repetitive atmospheric response from day to day. In PE, as defined here, precipitation extremes increase at rates beyond the Clausius‐Clapeyron rate. When analyzing causes for the increase, we find the variance in near‐surface temperature to increase significantly as precipitation builds up throughout the day and that this temperature variance is larger when surface heating is increased. We propose that enhanced rain evaporation may drive a feedback, by which cold pool activity, and the possible collision of cold pool gust fronts, is strengthened—thereby intensifying subsequent convective updrafts and their precipitation. [ABSTRACT FROM AUTHOR]

Abstract: A squall line on 22 May 2014 during the Southern China Monsoon Rainfall Experiment period is simulated with four bulk microphysical parameterizations (BMPs) using the Weather Research and Forecasting (WRF) model. Although most BMPs are able to capture the basic features of the squall line, the movement, morphology, and especially the length of the simulated squall lines differ significantly among BMPs. Morrison scheme tends to simulate a slower moving squall line with a weaker cold pool and better trailing stratiform cloud and precipitation due to the smaller snow fall speed and faster generation of snow particles than other schemes. Assuming hail or graupel in different schemes could result in different melting profiles of rimed‐ice particles, with hail melted substantially below the 0°C isotherm and contributing to the cold pool production significantly in WRF double‐moment six‐class microphysics scheme because of its use of larger fall speed for hail. Although ice‐phase particles simulated differ significantly among BMPs, it is rain evaporation that dominates the cold pool generation and maintenance of the squall line in this case. Stronger rain evaporation generally contributes to stronger cold pools and thus faster movement and longer simulated squall lines. Failure of the Stony Brook University‐YLin scheme in capturing the squall line was identified to be related to the turnoff of rain evaporation once environmental relative humidity is larger than 90%. With modifications of rain evaporation calculation and saturation adjustment method, the scheme is able to simulate this squall line reasonably well. [ABSTRACT FROM AUTHOR]

We investigated the effects of light-emitting diodes (LEDs) on physiological stress and immunity in black rockfish Sebastes schlegelii subjected to water temperature change [20 (normal temperature) → 14 → 20 °C] using progressive stepwise decline [experiment (Exp.) I; 2 °C/day] and direct decline (Exp. II; immediate exposure) in water temperature. We measured stress-related parameters such as cortisol, glucose, heat shock protein 70 and Na/K-ATPase, and immune parameters such as immunoglobulin M and lysozyme. We confirmed nuclear DNA damage using a comet assay. Physiological stress indicators were significantly higher, immune parameters were significantly lower, and the amount of nuclear DNA damage was higher after exposure to low temperatures, but these effects were mitigated by exposure to green or blue LEDs. The direct decline in temperature induced more physiological stress and nuclear DNA damage than the progressive stepwise change. Green and blue LEDs aid recovery from physiological damage in fish. [ABSTRACT FROM AUTHOR]

During summer, distinctive, bottom-trapped, cold water mass of remnant local and remote winter water called Cold Pool Water (CPW) resides as a swath over the mid to outer continental shelf throughout much of the Mid-Atlantic Bight (MAB). This evolving CPW is important because it strongly influences the ecosystem, including several important fisheries. Thus, there is a priority to better understand the relevant ocean processes and develop CPW forecast capability. Over the past decade, repeated high-resolution Slocum glider measurements of ocean water properties along a New Jersey cross-shelf transect have helped to define the variability of the CPW structure off New Jersey. More recently the Mid-Atlantic Regional Association Coastal Ocean Observing System-supported ocean gliders have occupied a series of along-shelf zigzag trajectories from Massachusetts to New Jersey and New Jersey to Maryland. The comprehensive set of March through November 2007 glider measurements has been used to define the annual evolution of the 10 °C Cold Pool in terms of its distribution and water properties. The rather steady warming at the rate of 1 °C per month July through October 2007 is reflected in the 2007 CPW temperature (T) and salinity (S) properties. We describe how a three-glider fleet view of the September 2013 Cold Pool (a) confirmed the Lentz (2017) CPW cold patch and (b) the impingement of a Gulf Stream warm core ring warmed and salted the 2013 CPW. The Gulf Sream 2013 event forced our extension of the CPW T and S properties. • Glider measurements reveal that the minimum Cold Pool temperature is close to the Mid-Atlantic Bight shelfbreak front. • Glider measurements define the 2007 Cold Pool Water, which warms at rates of 1°C and salts at 0.06 psu per month. • A trio of glider measured the extent and the volume of a 12 °C Cold Pool volume estimates over the Mid-Atlantic Bight. • The defining isotherm of the Cold Pool was increased from the historical 10°C–12°C. • The warming/salting effects of a Gulf Stream Warm Core Ring expanded the TS property definition of the Cold Pool Water. [ABSTRACT FROM AUTHOR]