Surface thermal inversion evolution in the bottom of a Pyrenean valley studied by observations and mesoscale simulations

2020 ◽  
Author(s):  
Maria A. Jiménez ◽  
Joan Cuxart ◽  
Alexandre Paci ◽  
Laura Conangla ◽  
Daniel Martínez-Villagrasa ◽  
...  
Keyword(s):  
Surface Fluxes ◽  
Cold Pool ◽  
Daily Cycle ◽  
Bottom Part ◽  
Thermal Inversion ◽  
Main Site ◽  
Variable Surface ◽  
Low Levels ◽  
Small Cloud ◽  
Mesoscale Simulations

<p>Two experimental campaigns have been carried out in the Cerdanya valley at south side of the Pyrenees (E-W oriented, 35 km long and 9 km wide) during fall 2015 (Cerdanya Cold Pool experiment, CCP’15) and winter 2017 (CCP’17, as a part of the Cerdanya-2017 experiment) to study the cold pool that usually forms there at night. The main site (Das) is placed in the central bottom part of the basin. Conangla et al (2018, IJOC) showed that most cold pool events reported there have a daily cycle, being formed in the evening and destroyed by solar heating of the surface the morning after.</p><p>The availability of vertical soundings performed by a tethered balloon and a WindRASS, together with measured surface fluxes of latent and sensible heat and momentum at the surface layer allows to inspect the establishment and evolution of the surface thermal inversion in Das. This area collects also downslope and downvalley flows accumulating cold air in the valley along the night. The organization of the flow at low levels is studied through mesoscale simulations of some selected Intensive Operational Periods (IOPs) and the surface observations at different locations along and across the valley.</p><p>The selected IOPs comprise nights with only locally-generated winds and small cloud cover, and with variable surface state including grass, fresh snow and patches of old snow. The evolution of the strength and depth of the surface inversion as seen by the model are compared to the available data. Besides, the organization of the flow at low levels and the contribution of the air from the tributary valleys is analyzed in terms of temperature and wind speed budgets to properly characterize the differences in the strength of the cold pool for the selected studied IOPs.</p>

scholarly journals ENSO’s Impact on the Gap Wind Regions of the Eastern Tropical Pacific Ocean*

2012 ◽  
Vol 25 (10) ◽  
pp. 3549-3565 ◽  
Author(s):  
Michael A. Alexander ◽  
Hyodae Seo ◽  
Shang Ping Xie ◽  
James D. Scott
Keyword(s):  
Pacific Ocean ◽  
Boundary Conditions ◽  
El Niño ◽  
El Nino ◽  
Tropical Pacific ◽  
Surface Fluxes ◽  
Ocean Dynamics ◽  
Tropical Pacific Ocean ◽  
Variable Surface ◽  
Sst Anomalies

Abstract The recently released NCEP Climate Forecast System Reanalysis (CFSR) is used to examine the response to ENSO in the northeast tropical Pacific Ocean (NETP) during 1979–2009. The normally cool Pacific sea surface temperatures (SSTs) associated with wind jets through the gaps in the Central American mountains at Tehuantepec, Papagayo, and Panama are substantially warmer (colder) than the surrounding ocean during El Niño (La Niña) events. Ocean dynamics generate the ENSO-related SST anomalies in the gap wind regions as the surface fluxes damp the SSTs anomalies, while the Ekman heat transport is generally in quadrature with the anomalies. The ENSO-driven warming is associated with large-scale deepening of the thermocline; with the cold thermocline water at greater depths during El Niño in the NETP, it is less likely to be vertically mixed to the surface, particularly in the gap wind regions where the thermocline is normally very close to the surface. The thermocline deepening is enhanced to the south of the Costa Rica Dome in the Papagayo region, which contributes to the local ENSO-driven SST anomalies. The NETP thermocline changes are due to coastal Kelvin waves that initiate westward-propagating Rossby waves, and possibly ocean eddies, rather than by local Ekman pumping. These findings were confirmed with regional ocean model experiments: only integrations that included interannually varying ocean boundary conditions were able to simulate the thermocline deepening and localized warming in the NETP during El Niño events; the simulation with variable surface fluxes, but boundary conditions that repeated the seasonal cycle, did not.

Cold Pools and Their Influence on the Tropical Marine Boundary Layer

2017 ◽  
Vol 74 (4) ◽  
pp. 1149-1168 ◽  
Author(s):  
Simon P. de Szoeke ◽  
Eric D. Skyllingstad ◽  
Paquita Zuidema ◽  
Arunchandra S. Chandra
Keyword(s):  
Boundary Layer ◽  
Marine Boundary Layer ◽  
Sensible Heat Flux ◽  
Surface Flux ◽  
Active Phase ◽  
Surface Fluxes ◽  
Cold Pool ◽  
Madden Julian Oscillation ◽  
Cold Pools ◽  
Central Indian Ocean

Abstract Cold pools dominate the surface temperature variability observed over the central Indian Ocean (0°, 80°E) for 2 months of research cruise observations in the Dynamics of the Madden–Julian Oscillation (DYNAMO) experiment in October–December 2011. Cold pool fronts are identified by a rapid drop of temperature. Air in cold pools is slightly drier than the boundary layer (BL). Consistent with previous studies, cold pools attain wet-bulb potential temperatures representative of saturated downdrafts originating from the lower midtroposphere. Wind and surface fluxes increase, and rain is most likely within the ~20-min cold pool front. Greatest integrated water vapor and liquid follow the front. Temperature and velocity fluctuations shorter than 6 min achieve 90% of the surface latent and sensible heat flux in cold pools. The temperature of the cold pools recovers in about 20 min, chiefly by mixing at the top of the shallow cold wake layer, rather than by surface flux. Analysis of conserved variables shows mean BL air is composed of 51% air entrained from the BL top (800 m), 22% saturated downdrafts, and 27% air at equilibrium with the ocean surface. The number of cold pools, and their contribution to the BL heat and moisture, nearly doubles in the convectively active phase compared to the suppressed phase of the Madden–Julian oscillation.

Peering into the internal structure of cold pools and their interactions with a dense observational network

2021 ◽  
Author(s):  
Cathy Hohenegger ◽  
Jaemyeong Seo ◽  
Hannes Nevermann ◽  
Bastian Kirsch ◽  
Nima Shokri ◽  
...  
Keyword(s):  
Internal Structure ◽  
Land Surface ◽  
Surface Fluxes ◽  
Cold Pool ◽  
Convective Clouds ◽  
Cold Pools ◽  
Soil Sensors ◽  
Modelling Studies ◽  
Surface Network ◽  
Shed Light

<p>Melting and evaporation of hydrometeors in and below convective clouds generates cold, dense air that falls through the atmospheric column and spreads at the surface like a density current, the cold pool. In modelling studies, the importance of cold pools in controlling the lifecycle of convection has often been emphasized, being through their organization of the cloud field or through their sheer deepening of the convection. Larger, longer-lived cold pools benefit convection, but little is actually known on the size and internal structure of cold pools from observations as the majority of cold pools are too small to be captured by the operational surface network.  One aim of the field campaign FESSTVaL was to peer into the internal structure of cold pools and their interactions with the underlying land surface by deploying a dense network of surface observations. This network consisted of 80 self-designed cold pool loggers, 19 weather stations and 83 soil sensors deployed in an area of 15 km around Lindenberg. FESSTVaL took place from 17 May to 27 August 2021.</p> <p>In principle, cold pool characteristics are affected both by the atmospheric state, which fuels cold pools through melting and evaporation of hydrometeors, and the land surface, which acts to destroy cold pools through friction and warming by surface fluxes. In this talk, the measurements collected during FESSTVaL will be used to shed light on these interactions.  We are particularly interested to assess how homogeneous the internal structure of cold pools is and whether heterogeneities of the land surface imprint themselves on this internal structure. The results will be compared to available model simulations.</p>

scholarly journals Evolution of Pre- and Postconvective Environmental Profiles from Mesoscale Convective Systems during PECAN

2019 ◽  
Vol 147 (7) ◽  
pp. 2329-2354 ◽  
Author(s):  
Stacey M. Hitchcock ◽  
Russ S. Schumacher ◽  
Gregory R. Herman ◽  
Michael C. Coniglio ◽  
Matthew D. Parker ◽  
...  
Keyword(s):  
Potential Temperature ◽  
Cold Pool ◽  
Temperature Perturbation ◽  
Convective System ◽  
Equivalent Potential Temperature ◽  
Wind Maximum ◽  
Low Level ◽  
Equivalent Potential ◽  
Mesoscale Convective ◽  
Low Levels

Abstract During the Plains Elevated Convection at Night (PECAN) field campaign, 15 mesoscale convective system (MCS) environments were sampled by an array of instruments including radiosondes launched by three mobile sounding teams. Additional soundings were collected by fixed and mobile PECAN integrated sounding array (PISA) groups for a number of cases. Cluster analysis of observed vertical profiles established three primary preconvective categories: 1) those with an elevated maximum in equivalent potential temperature below a layer of potential instability; 2) those that maintain a daytime-like planetary boundary layer (PBL) and nearly potentially neutral low levels, sometimes even well after sunset despite the existence of a southerly low-level wind maximum; and 3) those that are potentially neutral at low levels, but have very weak or no southerly low-level winds. Profiles of equivalent potential temperature in elevated instability cases tend to evolve rapidly in time, while cases in the potentially neutral categories do not. Analysis of composite Rapid Refresh (RAP) environments indicate greater moisture content and moisture advection in an elevated layer in the elevated instability cases than in their potentially neutral counterparts. Postconvective soundings demonstrate significantly more variability, but cold pools were observed in nearly every PECAN MCS case. Following convection, perturbations range between −1.9 and −9.1 K over depths between 150 m and 4.35 km, but stronger, deeper stable layers lead to structures where the largest cold pool temperature perturbation is observed above the surface.

217 IMPROVEMENT OF INTRACYTOPLASMIC SPERM INJECTION EMBRYO DEVELOPMENT IN BOVINE USING HIGH CYSTEAMINE CONCENTRATION DURING IN VITRO MATURATION AND SPERM CO-CULTURE WITH CUMULUS-OOCYTE COMPLEXES

2016 ◽  
Vol 28 (2) ◽  
pp. 239
Author(s):  
N. G. Canel ◽  
M. Suvá ◽  
R. J. Bevacqua ◽  
D. F. Salamone
Keyword(s):  
Embryo Development ◽  
Intracytoplasmic Sperm Injection ◽  
In Vitro Maturation ◽  
Critical Role ◽  
Standard Condition ◽  
Bottom Part ◽  
Low Levels ◽  
Vitro Development ◽  
Sperm Decondensation

In bovine, the intracytoplasmic sperm injection (ICSI) technique remains inefficient probably because of low levels of male sperm decondensation. In species with frequent fertilization failure, high cysteamine (Cys) concentration during in vitro maturation (IVM) has been used to improve IVF. Cysteamine, a precursor of glutathione, plays a critical role on sperm decondensation. The aim of this work was to improve ICSI efficiency in bovine by (1) increasing endogenous glutathione levels from oocytes using high Cys during IVM; and (2) incubating sperm with cumulus-oocyte complexes (COC) before ICSI, to mimic the physiological capacitation process. In experiment 1, we tested the effect of high Cys concentrations during IVM over the development of IVF embryos. In experiment 2, we performed ICSI after IVM with 1 mM Cys, based on IVF results. The COC were collected from slaughtered cow ovaries and IVM for 21 h with 10, 1, and 0.5 mM Cys v. 0.1 mM Cys (standard condition). Then, IVF was performed using 16 × 106 sperm mL–1 for 5 h on BO medium. For ICSI, COC were IVM with 1 mM Cys (ICSI 1 mM groups), and sperm used for injection was previously incubated with COC for 3 h (Inc. groups), as was done for IVF. Sham and diploid parthenogenetic (PA Diplo) controls were also included. Metaphase II oocytes were selected for ICSI, and injected oocytes were activated by a 4-min exposure to 5 μM ionomycin, placed on TCM-199 for 3 h (except for PA Diplo) and treated with 2 mM DMAP for 3 h. For ICSI control groups, COC were matured using 0.1 mM Cys. All embryos were cultured in SOF medium. Cleavage and blastocyst rates were evaluated on Days 2 and 7 post-IVF/ICSI, respectively. The total cell numbers of blastocysts were counted at Day 7, after Hoechst 33342 staining. Results are shown in Table 1. In conclusion, an increase of 5- to 10-fold of Cys concentration during IVM was not detrimental for development to blastocyst after IVF. The use of 1 mM Cys during IVM combined with the use of sperm co-cultured wit IVM COC before sperm injection is a good strategy to improve in vitro development of bovine ICSI embryos. Table 1.Effect of 1 mM cysteamine (Cys) during IVM over the development of IVF bovine embryos (top part) and effect of 1 mM Cys during IVM over embryo development of ICSI embryos, using sperm previously incubated (Inc.) with COC (bottom part)

scholarly journals Simple Models of the Role of Surface Fluxes in Convective Cold Pool Evolution

2004 ◽  
Vol 61 (13) ◽  
pp. 1582-1595 ◽  
Author(s):  
A. N. Ross ◽  
A. M. Tompkins ◽  
D. J. Parker
Keyword(s):  
Surface Fluxes ◽  
Cold Pool ◽  
Simple Models

scholarly journals Assessment of parameters describing representativeness of air quality in-situ measurement sites

2010 ◽  
Vol 10 (8) ◽  
pp. 3561-3581 ◽  
Author(s):  
S. Henne ◽  
D. Brunner ◽  
D. Folini ◽  
S. Solberg ◽  
J. Klausen ◽  
...  
Keyword(s):  
Air Quality ◽  
Particle Dispersion ◽  
Surface Fluxes ◽  
Wind Fields ◽  
Mixing Ratios ◽  
Air Quality Measurements ◽  
Novel Approach ◽  
Variable Surface ◽  
Catchment Areas ◽  
Clustering Approach

Abstract. The atmospheric layer closest to the ground is strongly influenced by variable surface fluxes (emissions, surface deposition) and can therefore be very heterogeneous. In order to perform air quality measurements that are representative of a larger domain or a certain degree of pollution, observatories are placed away from population centres or within areas of specific population density. Sites are often categorised based on subjective criteria that are not uniformly applied by the atmospheric community within different administrative domains yielding an inconsistent global air quality picture. A novel approach for the assessment of parameters reflecting site representativeness is presented here, taking emissions, deposition and transport towards 34 sites covering Western and Central Europe into account. These parameters are directly inter-comparable among the sites and can be used to select sites that are, on average, more or less suitable for data assimilation and comparison with satellite and model data. Advection towards these sites was simulated by backward Lagrangian Particle Dispersion Modelling (LPDM) to determine the sites' average catchment areas for the year 2005 and advection times of 12, 24 and 48 h. Only variations caused by emissions and transport during these periods were considered assuming that these dominate the short-term variability of most but especially short lived trace gases. The derived parameters describing representativeness were compared between sites and a novel, uniform and observation-independent categorisation of the sites based on a clustering approach was established. Six groups of European background sites were identified ranging from generally remote to more polluted agglomeration sites. These six categories explained 50 to 80% of the inter-site variability of median mixing ratios and their standard deviation for NO2 and O3, while differences between group means of the longer-lived trace gas CO were insignificant. The derived annual catchment areas strongly depended on the applied LPDM and input wind fields, the catchment settings and the year of analysis. Nevertheless, the parameters describing representativeness showed considerably less variability than the catchment geometry, supporting the applicability of the derived station categorisation.

scholarly journals Slow Modes of the Equatorial Waveguide

2020 ◽  
Vol 77 (5) ◽  
pp. 1575-1582 ◽  
Author(s):  
Kerry Emanuel
Keyword(s):  
Low Frequency ◽  
Surface Flux ◽  
Kelvin Waves ◽  
Surface Fluxes ◽  
Full Spectrum ◽  
Planetary Scale ◽  
Surface Enthalpy ◽  
Small Cloud ◽  
Low Frequency Waves ◽  
Equatorial Rossby Waves

Abstract A recently developed linear model of eastward-propagating disturbances has two separate unstable modes: convectively coupled Kelvin waves destabilized by the wind dependence of the surface enthalpy flux, and slow, MJO-like modes destabilized by cloud–radiation interaction and driven eastward by surface enthalpy fluxes. This latter mode survives the weak temperature gradient (WTG) approximation and has a time scale dictated by the time it takes for surface fluxes to moisten tropospheric columns. Here we extend that model to include higher-order modes and show that planetary-scale low-frequency waves with more complex structures can also be amplified by cloud–radiation interactions. While most of these waves survive the WTG approximation, their frequencies and growth rates are seriously compromised by that approximation. Applying instead the assumption of zonal geostrophy results in a better approximation to the full spectrum of modes. For small cloud–radiation and surface flux feedbacks, Kelvin waves and equatorial Rossby waves are destabilized, but when these feedbacks are strong enough, the frequencies do not lie close to classical equatorial dispersion curves except in the case of higher-frequency Kelvin and Yanai waves. An eastward-propagating n = 1 mode, in particular, has a structure resembling the observed structure of the MJO.

The Formation of Moist Vortices and Tropical Cyclones in Idealized Simulations

2015 ◽  
Vol 72 (9) ◽  
pp. 3499-3516 ◽  
Author(s):  
Christopher A. Davis
Keyword(s):  
Tropical Cyclone ◽  
Surface Temperature ◽  
Cloud Model ◽  
Deep Convection ◽  
Surface Fluxes ◽  
Cold Pool ◽  
Cold Pools ◽  
Thermodynamic Stabilization ◽  
Uniform Background ◽  
The Relationship

Abstract The upscale aggregation of convection is used to understand the emergence of rotating, coherent midtropospheric structures and the subsequent process of tropical cyclone formation. The Cloud Model, version 1 (CM1), is integrated on an f plane with uniform sea surface temperature (SST) and prescribed uniform background flow. Deep convection is maintained by surface fluxes from an ocean with uniform surface temperature. Convection begins to organize simultaneously into moist and dry midtropospheric patches after 10 days. After 20 days, the patches begin to rotate on relatively small scales. Moist cyclonic vortices merge, eventually forming a single dominant vortex that subsequently forms a tropical cyclone on a realistic time scale of about 5 days. Radiation that interacts with clouds and water vapor aids in forming coherent rotating structures. Using the path to genesis provided by the aggregated solution, the relationship between thermodynamic changes within the vortex and changes in the character of convection prior to genesis is explored. Consistent with previous studies, the approach to saturation within the midtropospheric vortex accelerates the genesis process. A novel result is that, prior to genesis, downdrafts become widespread and somewhat stronger. The increased downdraft mass flux leads to stronger and larger surface cold pools. Shear–cold pool dynamics promote the organization of lower-tropospheric updrafts that spin up the surface vortex. It is inferred that the observed inconsistency between convective intensity and thermodynamic stabilization prior to genesis results from sampling limitations of the observations wherein the important cold pool gradients are unresolved.

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