scholarly journals INVENTORY OF AFRICAN DESERT DUST EVENTS IN THE NORTH-CENTRAL IBERIAN PENINSULA IN 2003–2014 BASED ON SUNPHOTOMETER-AERONET AND PARTICULATE MASS-EMEP DATA

2016 ◽  
Author(s):  
V. E. Cachorro ◽  
M. A. Burgos ◽  
D. Mateos ◽  
C. Toledano ◽  
Y. Bennouna ◽  
...  
Keyword(s):  
Mineral Dust ◽  
Western Mediterranean ◽  
Human Observer ◽  
North Central ◽  
Desert Dust ◽  
The North ◽  
Western Mediterranean Basin ◽  
Synoptic Conditions ◽  
Particulate Mass ◽  
The Impact

Abstract. A reliable identification of Desert Dust (DD) episodes over North-central Spain is carried out based on AErosol RObotic NETwork (AERONET) columnar aerosol sun-photometer (aerosol optical depth, AOD, and Ångström exponent, α) and European Monitoring and Evaluation Programme (EMEP) surface particulate mass concentration (PMx, x = 10, 2.5, and 2.5–10 µm) as main core data. The impact of DD on background aerosol conditions is detectable by means of aerosol load thresholds and complementary information provided by HYSPLIT (Hybrid Single Particle Lagrangian Integrated Trajectory Model) air mass back-trajectories, MODIS (Moderate Resolution Imaging Spectroradiometer) images, forecasting aerosol models, and synoptic maps, which had been carefully reviewed by a human observer for each day included in the DD inventory. This identification method allows the detection of low and moderate DD intrusions and also mixtures of mineral dust with other aerosol types by means of the analysis of α. During the period studied (2003–2014), a total of 152 DD episodes composed of 419 days are identified. Overall, this means ~ 13 episodes and ~ 35 days per year with DD intrusion, representing 9.6 % days/year. During the identified DD outbreaks, 19 daily exceedances over 50 µg m−3 are reported at the surface. The occurrence of DD event days along the year peaks in March and June with a marked minimum in April and lowest occurrence in winter. A large inter-annual variability is observed showing a statistically significant temporal decreasing trend of ~3 days/year. As a key point, the DD impact on the aerosol climatology is addressed by evaluating the DD contribution to AOD, PM10, PM2.5, and PM2.5–10 obtaining mean values of 0.015 (11.5 %), 1.3 µg m−3 (11.8 %), 0.55 µg m−3 (8.5 %) and 0.79 µg m−3 (16.1 %), respectively. Almost similar annual cycles of DD contribution are obtained for AOD and PM10 with two maxima, one in summer (0.03 and 2.4 µg m−3 for AOD in June and PM10 in August, respectively) and another in March (0.02 for AOD and 2.2 µg m−3 for PM10), discrepancies occurring only in July and September. It is worth mentioning that the seasonal cycle of DD contribution to AOD does not follow the pattern of the total AOD (near bell shape), meanwhile both PM10 cycles (total and DD contribution) present more similar shapes between them, although a main discrepancy is observed in September. The inter-annual evolution of the DD contribution to AOD and PM10 has evidenced a progressive decrease. This decline in the levels of natural mineral dust aerosols can explain up to the 30 % of the total aerosol load decrease observed in the study area during the period 2003–2014. The relationship between columnar and surface DD contributions is evident with a correlation coefficient of 0.81 for the inter-annual averages. Finally, synoptic conditions during DD events are also analysed observing that the North African thermal low causes most of the events (~ 53 %). The results presented in this study highlight the relevance of the area studied since it can be considered as representative of the clean background in Western Mediterranean Basin where DD events have a high impact on aerosol load levels.

scholarly journals Inventory of African desert dust events in the north-central Iberian Peninsula in 2003–2014 based on sun-photometer–AERONET and particulate-mass–EMEP data

2016 ◽  
Vol 16 (13) ◽  
pp. 8227-8248 ◽  
Author(s):  
Victoria E. Cachorro ◽  
Maria A. Burgos ◽  
David Mateos ◽  
Carlos Toledano ◽  
Yasmine Bennouna ◽  
...  
Keyword(s):  
Mineral Dust ◽  
Human Observer ◽  
North Central ◽  
Desert Dust ◽  
The North ◽  
Western Mediterranean Basin ◽  
Synoptic Conditions ◽  
Particulate Mass ◽  
Sun Photometer ◽  
The Impact

Abstract. A reliable identification of desert dust (DD) episodes over north-central Spain is carried out based on the AErosol RObotic NETwork (AERONET) columnar aerosol sun photometer (aerosol optical depth, AOD, and Ångström exponent, α) and European Monitoring and Evaluation Programme (EMEP) surface particulate-mass concentration (PMx, x = 10, 2.5, and 2.5–10 µm) as the main core data. The impact of DD on background aerosol conditions is detectable by means of aerosol load thresholds and complementary information provided by HYSPLIT (Hybrid Single Particle Lagrangian Integrated Trajectory Model) air mass back trajectories, MODIS (Moderate Resolution Imaging Spectroradiometer) images, forecast aerosol models, and synoptic maps, which have been carefully reviewed by a human observer for each day included in the DD inventory. This identification method allows the detection of low and moderate DD intrusions and also of mixtures of mineral dust with other aerosol types by means of the analysis of α. During the period studied (2003–2014), a total of 152 DD episodes composed of 418 days are identified. Overall, this means ∼ 13 episodes and ∼ 35 days per year with DD intrusion, representing 9.5 % days year−1. During the identified DD intrusions, 19 daily exceedances over 50 µg m−3 are reported at the surface. The occurrence of DD event days during the year peaks in March and June, with a marked minimum in April and lowest occurrence in winter. A large interannual variability is observed showing a statistically significant temporal decreasing trend of ∼ 3 days year−1. The DD impact on the aerosol climatology is addressed by evaluating the DD contribution in magnitude and percent (in brackets) for AOD, PM10, PM2.5, and PM2.5 − 10, obtaining mean values of 0.015 (11.5 %), 1.3 µg m−3 (11.8 %), 0.55 µg m−3 (8.5 %) and 0.79 µg m−3 (16.1 %), respectively. Annual cycles of the DD contribution for AOD and PM10 present two maxima – one in summer (0.03 and 2.4 µg m−3 for AOD in June and PM10 in August) and another in March (0.02 for AOD and 2.2 µg m−3 for PM10) – both displaying a similar evolution with exceptions in July and September. The seasonal cycle of the DD contribution to AOD does not follow the pattern of the total AOD (close to a bell shape), whereas both PM10 cycles (total and DD contribution) are more similar to each other in shape, with an exception in September. The interannual evolution of the DD contribution to AOD and PM10 has evidenced a progressive decrease. This decline in the levels of mineral dust aerosols can explain up to 30 % of the total aerosol load decrease observed in the study area during the period 2003–2014. The relationship between columnar and surface DD contribution shows a correlation coefficient of 0.81 for the interannual averages. Finally, synoptic conditions during DD events are also analysed, observing that the north African thermal low causes most of the events ( ∼  53 %). The results presented in this study highlight the relevance of the area studied since it can be considered representative of the clean background in the western Mediterranean Basin where DD events have a high impact on aerosol load levels.

scholarly journals Potential deployment of offshore bottom pressure gauges and adoption of data assimilation for tsunami warning system in the western Mediterranean Sea

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Mohammad Heidarzadeh ◽  
Yuchen Wang ◽  
Kenji Satake ◽  
Iyan E. Mulia
Keyword(s):  
Data Assimilation ◽  
Warning System ◽  
Western Mediterranean ◽  
Tsunami Warning ◽  
Sensitivity Analyses ◽  
Bottom Pressure ◽  
Tsunami Warning System ◽  
Earthquake Scenarios ◽  
The North ◽  
Western Mediterranean Basin

AbstractWestern Mediterranean Basin (WMB) is among tsunamigenic zones with numerous historical records of tsunami damage and deaths. Most recently, a moderate tsunami on 21 May 2003 offshore Algeria, North Africa, was a fresh call for strengthening tsunami warning capabilities in this enclosed water basin. Here, we propose to deploy offshore bottom pressure gauges (OBPGs) and to adopt the framework of a tsunami data assimilation (TDA) approach for providing timely tsunami forecasts. We demonstrate the potential enhancement of the tsunami warning system through the case study of the 2003 Algeria tsunami. Four scenarios of OBPG arrangements involving 10, 5, 3 and 2 gauges are considered. The offshore gauges are located at distances of 120–300 km from the North African coast. The warning lead times are 20, 30, 48 and 55 min for four points of interest considered in this study: Ibiza, Palma, Sant Antoni and Barcelona, respectively. The forecast accuracies are in the range of 69–85% for the four OBPG scenarios revealing acceptable accuracies for tsunami warnings. We conclude that installation of OBPGs in the WMB can be helpful for providing successful and timely tsunami forecasts. We note that the OBPG scenarios proposed in this study are applicable only for the case of the 2003 Algeria tsunami. Further studies including sensitivity analyses (e.g., number of OBPG stations; earthquake magnitude, strike, epicenter) are required in order to determine OBPG arrangements that could be useful for various earthquake scenarios in the WMB.

A Synoptic Study on the Formation of Squall Lines in the North Central United States

1955 ◽  
Vol 36 (8) ◽  
pp. 390-396 ◽  
Author(s):  
John M. Porter ◽  
L. L. Means ◽  
J. E. Hovde ◽  
W. B. Chappell
Keyword(s):  
United States ◽  
Squall Line ◽  
Line Formation ◽  
Check List ◽  
North Central ◽  
The North ◽  
Squall Lines ◽  
Synoptic Conditions ◽  
Central United States

The aim of this study was to discover synoptic conditions which favored squall-line formation in the north-central United States. The squall lines over approximately a three-year period were classified into three types and studied using charts from the surface to 200 mb. Although the various parameters were not reduced to a strictly objective technique, a check list of significant parameters was prepared for the use and guidance of forecasters. It is believed that this check sheet will help the forecaster in forecasting squall-line development in the north-central United States.

scholarly journals Understanding Precipitation Changes in Iberia in Early Spring: Weather Typing and Storm-Tracking Approaches

2006 ◽  
Vol 7 (1) ◽  
pp. 101-113 ◽  
Author(s):  
Daniel Paredes ◽  
Ricardo M. Trigo ◽  
Ricardo Garcia-Herrera ◽  
Isabel Franco Trigo
Keyword(s):  
Iberian Peninsula ◽  
North Atlantic ◽  
Large Scale ◽  
Western Mediterranean ◽  
Early Spring ◽  
The North ◽  
Western Mediterranean Basin ◽  
The North Atlantic ◽  
Circulation Changes ◽  
Precipitation Trends

Abstract March monthly accumulated precipitation in the central and western regions of the Iberian Peninsula presents a clear continuous decline of 50% during the 1960–97 period. A finer analysis using daily data reveals that this trend is exactly confined to the month of March. However, this is merely the most visible aspect of a larger phenomenon over the North Atlantic/European sector. The European precipitation trends in March for the period 1960–2000 show a clear distribution of increasing precipitation in the northern regions (the British Isles and parts of Scandinavia) together with decreasing trends throughout the western Mediterranean Basin. Relevant circulation changes over the North Atlantic and European sectors explain these precipitation trends. First, a regional Eulerian approach by means of a weather-type (WT) classification shows that the major rainfall contributors in March display significantly decreasing frequencies for the Iberian Peninsula, in contrast to the corresponding “wet” weather types for the U.K./Ireland sector, which display increasing frequencies. Within a larger context, a Lagrangian approach, based on the analysis of storm tracks over Europe and the North Atlantic region, reveals dramatic changes in the location of cyclones in the last four decades that coincide with the corresponding precipitation trends in Europe. The North Atlantic Oscillation is suggested to be the most important large-scale factor controlling both the circulation changes and the precipitation trends over the Euro–Atlantic area in March. Finally, the potential impact of reduced precipitation for rivers and water resources in the Iberian Peninsula is considered.

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