Convection-circulation interactions over West Africa in simulations with explicit and parameterised convection

2021 ◽  
Author(s):  
Francesca Morris ◽  
Juliane Schwendike ◽  
Doug Parker ◽  
Caroline Bain
Keyword(s):  
West Africa ◽  
High Impact ◽  
Diurnal Changes ◽  
Freezing Level ◽  
Diurnal Patterns ◽  
High Impact Weather ◽  
The Mean ◽  
Regional Forecasts ◽  
Synoptic Circulation ◽  
Natural Laboratory

<p>This work examines the representation of convection-circulation coupling over tropical West Africa in convection-permitting models. Tropical West Africa is not only a region characterised by extremely high-impact weather, in the form of intense and frequent organised convection, but it is also a region of strong baroclinicity and wind shear, and therefore an excellent natural laboratory for examining the connections between mesoscale convection and synoptic circulations. Developing understanding of<sub></sub>convection-circulation coupling is crucial to informing development of convection parameterisations and improving regional forecasts of high-impact weather.</p><p>We evaluate output from the CP4-Africa configuration of the Met Office Unified Model to investigate links between convective activity and synoptic motions. To illustrate its strengths in representing convection-circulation feedbacks, CP4 output is compared to that from a similar UM configuration which uses a convection parameterisation.</p><p>We examine the mean diurnal cycle of circulation during the storm season. Distinct diurnal patterns in circulation tendency are compared to patterns in updraughts and precipitation, which illustrate different forms of convection which can be observed at different points during the day. A “congestus” mode convects up to around the freezing level from morning until early evening, while deep organised convection triggers in the mid-to-late afternoon and persists overnight. The two forms of convection appear to cause characteristically different responses in the synoptic circulation.</p><p>To confirm which physical processes cause changes to circulation in the region, we calculate terms in the circulation tendency equation. Separating these terms into mean and eddy-flux contributions allows us to establish the extent to which mesoscale systems and synoptic structures each influence the diurnal changes to circulation.</p>

scholarly journals Nonlinear Characteristics of Ensemble Perturbation Evolution and Their Application to Forecasting High-Impact Events

2013 ◽  
Vol 28 (6) ◽  
pp. 1353-1365 ◽  
Author(s):  
Brian C. Ancell
Keyword(s):  
Weather Prediction ◽  
Ensemble Member ◽  
High Impact ◽  
Synoptic Scale ◽  
Wind Speeds ◽  
Weather Events ◽  
Ensemble Mean ◽  
High Impact Weather ◽  
The Mean ◽  
Impact Events

Abstract Ensemble forecasting is becoming an increasingly important aspect of numerical weather prediction. As ensemble perturbation evolution becomes more nonlinear as a forecast evolves, the ensemble mean can diverge from the model attractor on which ensemble members are constrained. In turn, the ensemble mean can become increasingly unrealistic, and although statistically best on average, it can provide poor forecast guidance for specific high-impact events. This study uses an ensemble Kalman filter to investigate this behavior at the synoptic scale for landfalling midlatitude cyclones. This work also aims to understand the best way to select “best members” closest to the mean that both behave realistically and possess the statistically beneficial qualities of the mean. It is found that substantial nonlinearity emerges within forecast times of a day, which roughly agrees with previous research addressing synoptic-scale nonlinearity more generally. The evolving nonlinearity results in unrealistic behavior of the ensemble mean that significantly underestimates precipitation and wind speeds associated with the cyclones. Choosing a single ensemble member closest to the ensemble mean over the entire forecast window provides forecasts that are unable to produce the relatively small errors of the ensemble mean. However, since different ensemble members are closest to the ensemble mean at different forecast times, the best forecast is composed of different ensemble members throughout the forecast window. The benefits and limitations of applying this methodology to improve forecasts of synoptic-scale high-impact weather events are discussed.

scholarly journals A methodology to conduct wind damage field surveys for high-impact weather events of convective origin

2020 ◽  
Vol 20 (5) ◽  
pp. 1513-1531 ◽  
Author(s):  
Oriol Rodríguez ◽  
Joan Bech ◽  
Juan de Dios Soriano ◽  
Delia Gutiérrez ◽  
Salvador Castán
Keyword(s):  
Field Studies ◽  
High Impact ◽  
Strong Wind ◽  
Field Surveys ◽  
Weather Events ◽  
Straight Line ◽  
High Impact Weather ◽  
Strong Winds ◽  
Wind Events ◽  
The One

Abstract. Post-event damage assessments are of paramount importance to document the effects of high-impact weather-related events such as floods or strong wind events. Moreover, evaluating the damage and characterizing its extent and intensity can be essential for further analysis such as completing a diagnostic meteorological case study. This paper presents a methodology to perform field surveys of damage caused by strong winds of convective origin (i.e. tornado, downburst and straight-line winds). It is based on previous studies and also on 136 field studies performed by the authors in Spain between 2004 and 2018. The methodology includes the collection of pictures and records of damage to human-made structures and on vegetation during the in situ visit to the affected area, as well as of available automatic weather station data, witness reports and images of the phenomenon, such as funnel cloud pictures, taken by casual observers. To synthesize the gathered data, three final deliverables are proposed: (i) a standardized text report of the analysed event, (ii) a table consisting of detailed geolocated information about each damage point and other relevant data and (iii) a map or a KML (Keyhole Markup Language) file containing the previous information ready for graphical display and further analysis. This methodology has been applied by the authors in the past, sometimes only a few hours after the event occurrence and, on many occasions, when the type of convective phenomenon was uncertain. In those uncertain cases, the information resulting from this methodology contributed effectively to discern the phenomenon type thanks to the damage pattern analysis, particularly if no witness reports were available. The application of methodologies such as the one presented here is necessary in order to build homogeneous and robust databases of severe weather cases and high-impact weather events.

scholarly journals Diurnal Body Temperature and Rate of Passage of Loggers in Lions

Animals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 1388
Author(s):  
Ted Friend ◽  
Giulia Corsini ◽  
Vincent Manero ◽  
Raffaella Cocco
Keyword(s):  
Body Temperature ◽  
Time Frame ◽  
Heat Lamp ◽  
Future Studies ◽  
Ambient Temperatures ◽  
Diurnal Patterns ◽  
Data Loggers ◽  
The Mean ◽  
African Lions ◽  
Circadian Patterns

The documentation of diurnal patterns in body temperature in lions could be important because disruption of circadian patterns can be a useful measure of distress. This study quantified changes in body temperature of seven African lions (Panthera leo) at 5 min intervals during cold conditions from noon until the ingested body temperature loggers were expelled the next day. Thirteen loggers were fed to 11 lions during their daily noon feeding, while ambient temperatures were also recorded using six data loggers. The lions had continuous access to their dens and exercise pens during the day but were restricted to their heavily bedded dens that also contained a heat lamp from 23:00 until 08:00 the next day. Body temperatures averaged 37.95 ± 0.42 °C at 15:50, and 36.81 ± 0.17 °C at 06:50 the next day, 30 min before the first loggers passed from a lion, and were significantly different (t-test, t = 8.09, df = 6, p < 0.0003). The mean duration for the time of passage was 22 ± 2.69 (h ± SD), so future studies using the noninvasive feeding of temperature loggers need to consider that time frame.

Diurnal changes in the plasma concentrations of LH and hypothalamic contents of LHRH-I and LHRH-II in the domestic hen

1991 ◽  
Vol 130 (3) ◽  
pp. 457-462 ◽  
Author(s):  
S. C. Wilson ◽  
R. T. Gladwell ◽  
F. J. Cunningham
Keyword(s):  
Plasma Concentration ◽  
Diurnal Rhythm ◽  
Laying Hens ◽  
Plasma Concentrations ◽  
Posterior Hypothalamus ◽  
Anterior Hypothalamus ◽  
Diurnal Changes ◽  
The Mean ◽  
The Times ◽  
Lh Secretion

ABSTRACT Diurnal changes of LH secretion in sexually immature hens of 9, 11, 13 and 15 weeks of age consisted of 25–40% increases in the mean concentrations of LH in plasma between 15.00 and 18.00 h, i.e. between 2 h before and 1 h after the onset of darkness. During this time there was a tendency for the mean contents of LHRH-I in the anterior hypothalamus and posterior hypothalamus to increase by 21–74% and 20–56% respectively. In hens of 9 and 15 weeks, diurnal changes in the plasma concentration of LH closely paralleled those of LHRH-I content in the posterior hypothalamus. In contrast, the diurnal rhythm of LH secretion in hens of 11 and 13 weeks was more marked and plasma concentrations of LH continued to rise steeply between 18.00 and 21.00 h, i.e. between 1 and 4 h after the onset of darkness. At 11 weeks, this was associated with a reduction (P<0·01) in the contents of LHRH-I and LHRH-II, particularly in the anterior hypothalamus. In laying hens, a diurnal decline (P<0·01) in the plasma concentration of LH between 1 and 4 h after the onset of darkness was preceded by a fall (P<0·05) in the content of LHRH-I in the posterior hypothalamus and in the total hypothalamic content of LHRH-II (P<0·01). In all groups of hens, irrespective of the times of day at which tissue was taken, significant (P<0·05–<0·001) correlations between the contents of LHRH-I and LHRH-II in the anterior hypothalamus were observed. It is concluded that a diurnal rhythm of release of LHRH-I may drive the diurnal rhythm of LH secretion. Thus, in sexually immature hens of 9 and 15 weeks and laying hens in which diurnal changes in plasma LH were small there were parallel changes in the content of LHRH-I in the posterior hypothalamus. However, where the plasma concentration of LH was increased substantially, as at 11 weeks, there was a decline in the hypothalamic contents of LHRH-I. A simultaneous fall in the hypothalamic content of LHRH-II raises the possibility of a causal relationship between the activities of LHRH-II, LHRH-I and the release of LH. Journal of Endocrinology (1991) 130, 457–462

scholarly journals Tidal and seasonal carbon and nutrient dynamics of the Guadalquivir estuary and the Bay of Cádiz (SW Iberian Peninsula)

2013 ◽  
Vol 10 (7) ◽  
pp. 4481-4491 ◽  
Author(s):  
M. Ribas-Ribas ◽  
E. Anfuso ◽  
A. Gómez-Parra ◽  
J. M. Forja
Keyword(s):  
Continental Shelf ◽  
Nutrient Dynamics ◽  
Diurnal Changes ◽  
Gulf Of Cadiz ◽  
Mean Velocity ◽  
Guadalquivir Estuary ◽  
Gulf Of Cádiz ◽  
The Mean ◽  
Bay Of Cadiz ◽  
Bay Of Cádiz

Abstract. To study the effects of the physical environment on carbon and nutrient cycle dynamics on the north-eastern shelf of the Gulf of Cádiz, changes in currents, tides, salinity, temperature, carbon system parameters (fugacity of CO2 (fCO2), dissolved organic carbon, dissolved inorganic carbon (DIC) and pH) and other related parameters(dissolved oxygen, total dissolved nitrogen (TDN), nutrients and suspended particulate matter) were measured in transects across the Guadalquivir estuary and Bay of Cádiz mouths. The main objective of this study is to investigate the influence of these inner ecosystems on the carbon and nutrient distributions on the adjacent continental shelf. Three cruises were undertaken in June 2006, November 2006 and February 2007. During the whole study period, Guadalquivir estuary exported components at a rate of 3 Gmol of SiO2, 4 Gmol of DIN, 3 Gmol of TDN, 31 Gmol of DOC and 604 Gmol of DIC per year. On the other hand, Bay of Cádiz imported 3 Gmol of SiO2, 1 Gmol of DIN, 2 Gmol of TDN, 33 Gmol of DOC and 562 Gmol of DIC per year. Diurnal variability of fCO2 could have a potentially important implication on the estimate of air–sea CO2 fluxes. Tides influence velocity and transport of carbon and nutrients: we found statistically significant differences (p < 0.0001, n = 220) between the flood tide (the mean velocity was 4.85 cm s–1) and the ebb tide (the mean velocity was −5.67 cm s–1). Biological activity and diurnal changes have also an important role on the carbon and nutrient dynamics. Seasonal carbon and nutrient variations were found. During June, both systems were exporting components to the adjacent continental shelf of the Gulf of Cádiz, whereas in February both systems were importing. Monthly studies should be undertaken to completely understand this dynamic system.

A role of high impact weather events in waterborne disease outbreaks in Canada, 1975 – 2001

2006 ◽  
Vol 16 (3) ◽  
pp. 167-180 ◽  
Author(s):  
Kate M. Thomas ◽  
Dominique F. Charron ◽  
David Waltner-Toews ◽  
Corinne Schuster ◽  
Abdel R. Maarouf ◽  
...  
Keyword(s):  
Disease Outbreaks ◽  
High Impact ◽  
Waterborne Disease ◽  
Weather Events ◽  
High Impact Weather

scholarly journals Projected changes in crop yield mean and variability over West Africa in a world 1.5 K warmer than the pre-industrial

2017 ◽  
Author(s):  
Ben Parkes ◽  
Dimitri Defrance ◽  
Benjamin Sultan ◽  
Philippe Ciais ◽  
Xuhui Wang
Keyword(s):  
Climate Change ◽  
West Africa ◽  
Rainwater Harvesting ◽  
High Temperature Stress ◽  
Climate Projections ◽  
Maize Crop ◽  
Crop Models ◽  
Time Frequency ◽  
The Mean ◽  
Near Term

Abstract. The ability of a country or region to feed itself in the upcoming decades is a question of importance. The population in West Africa is expected to increase significantly in the next 30 years. The responses of food crops to short term climate change is therefore critical to the population at large and the decision makers tasked with providing food for their people. An ensemble of near term climate projections are used to simulate maize, millet and sorghum in West Africa in the recent historic and near term future. The mean yields are not expected to alter significantly, while there is an increase in inter annual variability. This increase in variability increases the likelihood of crop failures, which are defined as yield negative anomalies beyond one standard deviation during a period of 20 years. The increasing variability increases the frequency and intensity of crop failures across West Africa. The mean return frequency between mild maize crop failures from process based crop models increases from once every 6.8 years to once every 4.5 years. The mean return time frequency for severe crop failures (beyond 1.5 standard deviations) also almost doubles from once every 16.5 years to once every 8.5 years. Two adaptation responses to climate change, the adoption of heat-resistant cultivars and the use of captured rainwater have been investigated using one crop model in an idealised sensitivity test. The generalised adoption of a cultivar resistant to high temperature stress during flowering is shown to be more beneficial than using rainwater harvesting by both increasing yields and the return frequency of crop failures.

scholarly journals The alternative of CubeSat-based advanced infrared and microwave sounders for high impact weather forecasting

2019 ◽  
Vol 12 (2) ◽  
pp. 80-90 ◽  
Author(s):  
Zhenglong LI ◽  
Jun LI ◽  
Timothy J. SCHMIT ◽  
Pei WANG ◽  
Agnes LIM ◽  
...  
Keyword(s):  
Weather Forecasting ◽  
High Impact ◽  
High Impact Weather

scholarly journals Effects of Site, Genotype and Subsequent Harvest Rotation on Willow Productivity

Agriculture ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 412 ◽  
Author(s):  
Mariusz Jerzy Stolarski ◽  
Michał Krzyżaniak ◽  
Dariusz Załuski ◽  
Józef Tworkowski ◽  
Stefan Szczukowski
Keyword(s):  
Survival Rate ◽  
Plant Height ◽  
Biomass Yield ◽  
High Impact ◽  
The Other ◽  
Plant Survival ◽  
Dry Biomass ◽  
The Mean ◽  
Very High ◽  
Biometric Features

Perennial crops harvested in short rotations provide substantial amounts of biomass. This study determined the survival rate, biometric features and yield of fresh and dry biomass of 15 willow genotypes (including seven varieties and eight clones), cultivated at two different sites in two consecutive three-year harvest rotations. The study revealed the very high impact of the genotype (81% of the total variance) on the willow yield. The harvest rotation, along with the genotype, had a significant impact on the plant survival rate and the number of shoots per stool. Willow biomass was mainly affected by the plant height, its survival rate and shoot diameter. The significantly highest fresh (106 Mg ha−1) and dry biomass yield (54.0 Mg ha−1) was obtained from the Żubr variety of S. viminalis, which distinguished this variety from the other genotypes. The mean yield for the best three and five genotypes was 13% and 17% lower, respectively, and the mean yield for the whole experiment was 37% lower compared to the mean yield of the best variety (Żubr). Therefore, the choice of a willow genotype is of key importance for successful willow production.

scholarly journals Inter-Comparison of AIRS Temperature and Relative Humidity Profiles with AMMA and DACCIWA Radiosonde Observations over West Africa

2020 ◽  
Vol 12 (16) ◽  
pp. 2631
Author(s):  
Marian Amoakowaah Osei ◽  
Leonard Kofitse Amekudzi ◽  
Craig R. Ferguson ◽  
Sylvester Kojo Danuor
Keyword(s):  
Relative Humidity ◽  
West Africa ◽  
Water Vapour ◽  
Radiosonde Data ◽  
Weather Information ◽  
Significant Difference ◽  
High Impact Weather ◽  
Mean Square Difference ◽  
June July ◽  
Humidity Profiles

The vertical profiles of temperature and water vapour from the Atmospheric InfraRed Sounder (AIRS) have been validated across various regions of the globe as an effort to provide a substitute for radiosonde observations. However, there is a paucity of inter-comparisons over West Africa where local convective processes dominate and radiosonde observations (RAOBs) are limited. This study validates AIRS temperature and relative humidity profiles for selected radiosonde stations in West Africa. Radiosonde data were obtained from the AMMA and DACCIWA campaigns which spanned 2006–2008 and June–July 2016 respectively and offered a period of prolonged radiosonde observations in West Africa. AIRS performance was evaluated with the bias and root mean square difference (RMSD) at seven RAOB stations which were grouped into coastal and inland. Evaluation was performed on diurnal and seasonal timescales, cloud screening conditions and derived thunderstorm instability indices. At all timescales, the temperature RMSD was higher than the AIRS accuracy mission goal of ±1 K. Relative humidity RMSD was satisfactory with deviations <20% and <50% for both lower and upper troposphere respectively. AIRS retrieval of water vapour under cloudy and cloud-free conditions had no significant difference whereas cloud-free temperature was found to be more accurate. The seasonal evolution of some thunderstorm convective indices were also found to be comparable for AIRS and RAOB. The ability of AIRS to capture the evolution of these indices imply it will be a useful dataset for the African Science for Weather Information and Forecasting Techniques (SWIFT) high impact weather studies.

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