scholarly journals Hot and cold flavors of southern California’s Santa Ana winds: their causes, trends, and links with wildfire

2021 ◽  
Author(s):  
Alexander Gershunov ◽  
Janin Guzman Morales ◽  
Benjamin Hatchett ◽  
Kristen Guirguis ◽  
Rosana Aguilera ◽  
...  
Keyword(s):  
Great Basin ◽  
Heat Waves ◽  
Early Warning Systems ◽  
High Amplitude ◽  
Warming Trend ◽  
Snow Accumulation ◽  
Burned Area ◽  
Rossby Wave Breaking ◽  
Santa Ana ◽  
Santa Ana Winds

AbstractSanta Ana winds (SAWs) are associated with anomalous temperatures in coastal Southern California (SoCal). As dry air flows over SoCal’s coastal ranges on its way from the elevated Great Basin down to sea level, all SAWs warm adiabatically. Many but not all SAWs produce coastal heat events. The strongest regionally averaged SAWs tend to be cold. In fact, some of the hottest and coldest observed temperatures in coastal SoCal are linked to SAWs. We show that hot and cold SAWs are produced by distinct synoptic dynamics. High-amplitude anticyclonic flow around a blocking high pressure aloft anchored at the California coast produces hot SAWs. Cold SAWs result from anticyclonic Rossby wave breaking over the northwestern U.S. Hot SAWs are preceded by warming in the Great Basin and dry conditions across the Southwestern U.S. Precipitation over the Southwest, including SoCal, and snow accumulation in the Great Basin usually precede cold SAWs. Both SAW flavors, but especially the hot SAWs, yield low relative humidity at the coast. Although cold SAWs tend to be associated with the strongest winds, hot SAWs tend to last longer and preferentially favor wildfire growth. Historically, out of large (> 100 acres) SAW-spread wildfires, 90% were associated with hot SAWs, accounting for 95% of burned area. As health impacts of SAW-driven coastal fall, winter and spring heat waves and impacts of smoke from wildfires have been recently identified, our results have implications for designing early warning systems. The long-term warming trend in coastal temperatures associated with SAWs is focused on January–March, when hot and cold SAW frequency and temperature intensity have been increasing and decreasing, respectively, over our 71-year record.

scholarly journals Santa Ana winds and predictors of wildfire progression in southern California

2014 ◽  
Vol 23 (8) ◽  
pp. 1119 ◽  
Author(s):  
Michael Billmire ◽  
Nancy H. F. French ◽  
Tatiana Loboda ◽  
R. Chris Owen ◽  
Marlene Tyner
Keyword(s):  
Wind Speed ◽  
Relative Humidity ◽  
Southern California ◽  
Burned Area ◽  
Strong Positive Correlation ◽  
Fuel Temperature ◽  
Fuel Loading ◽  
Fire Event ◽  
Santa Ana ◽  
Santa Ana Winds

Santa Ana winds have been implicated as a major driver of large wildfires in southern California. While numerous anecdotal reports exist, there is little quantitative analysis in peer-reviewed literature on how this weather phenomenon influences fire progression rates. We analysed fire progression within 158 fire events in southern California as a function of meteorologically defined Santa Ana conditions between 2001 and 2009. Our results show quantitatively that burned area per day is 3.5–4.5 times larger on Santa Ana days than on non-Santa Ana days. Santa Ana definition parameters (relative humidity, wind speed) along with other predictor variables (air temperature, fuel temperature, 10-h fuel moisture, population density, slope, fuel loading, previous-day burn perimeter) were tested individually and in combination for correlation with subsets of daily burned area. Relative humidity had the most consistently strong correlation with burned area per day. Gust and peak wind speed had a strong positive correlation with burned area per day particularly within subsets of burned area representing only the first day of a fire, >500 ha burned areas, and on Santa Ana days. The suite of variables comprising the best-fit generalised linear model for predicting burned area (R2 = 0.41) included relative humidity, peak wind speed, previous-day burn perimeter and two binary indicators for first and last day of a fire event.

scholarly journals A heat-health watch and warning system with extended season and evolving thresholds

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Mahamat Abdelkerim Issa ◽  
Fateh Chebana ◽  
Pierre Masselot ◽  
Céline Campagna ◽  
Éric Lavigne ◽  
...  
Keyword(s):  
Excess Mortality ◽  
Heat Waves ◽  
Meteorological Data ◽  
Warm Season ◽  
Warning System ◽  
Early Warning Systems ◽  
Climate Projections ◽  
Warning Systems ◽  
Extreme Heat Events ◽  
Watch And Warning System

Abstract Background Many countries have developed heat-health watch and warning systems (HHWWS) or early-warning systems to mitigate the health consequences of extreme heat events. HHWWS usually focuses on the four hottest months of the year and imposes the same threshold over these months. However, according to climate projections, the warm season is expected to extend and/or shift. Some studies demonstrated that health impacts of heat waves are more severe when the human body is not acclimatized to the heat. In order to adapt those systems to potential heat waves occurring outside the hottest months of the season, this study proposes specific health-based monthly heat indicators and thresholds over an extended season from April to October in the northern hemisphere. Methods The proposed approach, an adoption and extension of the HHWWS methodology currently implemented in Quebec (Canada). The latter is developed and applied to the Greater Montreal area (current population 4.3 million) based on historical health and meteorological data over the years. This approach consists of determining excess mortality episodes and then choosing monthly indicators and thresholds that may involve excess mortality. Results We obtain thresholds for the maximum and minimum temperature couple (in °C) that range from (respectively, 23 and 12) in April, to (32 and 21) in July and back to (25 and 13) in October. The resulting HHWWS is flexible, with health-related thresholds taking into account the seasonality and the monthly variability of temperatures over an extended summer season. Conclusions This adaptive and more realistic system has the potential to prevent, by data-driven health alerts, heat-related mortality outside the typical July–August months of heat waves. The proposed methodology is general and can be applied to other regions and situations based on their characteristics.

scholarly journals Dust Deposition on the Gulf of California Caused by Santa Ana Winds

Atmosphere ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 275 ◽  
Author(s):  
Christian A. Álvarez ◽  
José N. Carbajal ◽  
Luis F. Pineda-Martínez ◽  
José Tuxpan ◽  
David E. Flores
Keyword(s):  
Gulf Of California ◽  
Dust Emission ◽  
Positive Influence ◽  
Dust Particles ◽  
Weather Research And Forecasting ◽  
Western Coast ◽  
Emission Rates ◽  
Dust Deposition ◽  
Santa Ana ◽  
Santa Ana Winds

Numerical simulations revealed a profound interaction between the severe dust storm of 2007 caused by Santa Ana winds and the Gulf of California. The weather research and forecasting model coupled with a chemistry module (WRF-CHEM) and the hybrid single-particle Lagrangian integrated trajectory model (HYSPLIT) allowed for the estimation of the meteorological and dynamic aspects of the event and the dust deposition on the surface waters of the Gulf of California caused by the erosion and entrainment of dust particles from the surrounding desert regions. The dust emission rates from three chosen areas (Altar desert, Sonora coast, and a region between these two zones) and their contribution to dust deposition over the Gulf of California were analyzed. The Altar Desert had the highest dust emission rates and the highest contribution to dust deposition over the Gulf of California, i.e., it has the most critical influence with 96,879 tons of emission and 43,539 tons of dust deposition in the gulf. An increase of chlorophyll-a concentrations is observed coinciding with areas of high dust deposition in the northern and western coast of the gulf. This kind of event could have a significant positive influence over the mineralization and productivity processes in the Gulf of California, despite the soil loss in the eroded regions.

The Santa Ana Winds of Southern California

Weatherwise ◽  
1962 ◽  
Vol 15 (3) ◽  
pp. 102-121 ◽  
Author(s):  
Leo A. Sergius ◽  
George R. Ellis ◽  
Richard M. Ogden
Keyword(s):  
Southern California ◽  
Santa Ana ◽  
Santa Ana Winds

Relative contribution of Trend and Interannually-varying SST Anomalies to the 2018 Heat Waves in the Extratropical Northern Hemisphere

2021 ◽  
pp. 1-58
Author(s):  
Chi-Cherng Hong ◽  
Wang-Ling Tseng ◽  
Huang-Hsiung Hsu ◽  
Ming-Ying Lee ◽  
Chi-Chun Chang
Keyword(s):  
Northern Hemisphere ◽  
Heat Waves ◽  
Northeast Asia ◽  
Decomposition Analysis ◽  
Warming Trend ◽  
Singular Value Decomposition Analysis ◽  
Relative Contribution ◽  
Symmetric Perturbation ◽  
Prolonged Heat ◽  
Value Decomposition

AbstractThe northern extratropics—including regions in northern Europe, northeast Asia, and North America—experienced extremely prolonged heat waves during May–August 2018. Record-breaking surface temperatures, which caused numerous deaths, were observed in several cities. The 2018 heat waves exhibited a circumglobal characteristic owing to a circumpolar perturbation (CCP) in the middle–upper troposphere of the Northern Hemisphere (NH). The CCP had two parts: a wave-like perturbation and a hemispheric perturbation that was almost zonally symmetric. Singular value decomposition analysis revealed that the zonally symmetric perturbation was coupled to the SST warming trend, whereas the wave-like perturbation was primarily coupled to the interannually-varying SST anomaly (SSTA), particularly in the tropical North Pacific, which reached an extreme in 2018. Numerical experiments confirmed that the zonally symmetric component was primarily resulted from the SSTA associated with the warming trend, whereas the interannually-varying SSTAs in the NH contributed mostly to the wave-like perturbation. The warming trend component of SSTA, especially that in the tropics, compounded by the unusually large SSTAs in 2018, was hypothesized to have contributed to inducing the circumpolar circulation anomaly that caused the record-breaking heat waves in the extratropical NH in 2018.

scholarly journals Climate since AD 1510 on Dyer Plateau, Antarctic Peninsula: evidence for recent climate change

1994 ◽  
Vol 20 ◽  
pp. 420-426 ◽  
Author(s):  
L. G. Thompson ◽  
D. A. Peel ◽  
E. Mosley-thompson ◽  
R. Mulvaney ◽  
J. Dal ◽  
...  
Keyword(s):  
19Th Century ◽  
Antarctic Peninsula ◽  
Chemical Species ◽  
Ice Cores ◽  
Warming Trend ◽  
Snow Accumulation ◽  
Annual Variations ◽  
Recent Climate ◽  
The 19Th Century ◽  
The Antarctic

A 480 year record of the oxygen-isotope ratios, dust content, chemical species and net accumulation from ice cores drilled in 1989 90 on Dyer Plateau in the Antarctic Peninsula is presented. The continuous analyses of small (sub-annual) samples reveal well-preserved annual variations in both sulfate content and δ18O, thus allowing an excellent time-scale to be established.This history reveals a recent pronounced warming in which the last two decades have been among the warmest in the last five centuries. Furthermore, unlike in East Antarctica, on Dyer Plateau conditions appear to have been fairly normal from AD 1500 to 1850 with cooler conditions from 1850 to 1930 and a warming trend dominating since 1930. Reconstructed annual layer thicknesses suggest an increase in net accumulation beginning early in the 19th century and continuing to the present. This intuitive conflict between increasing net accumulation and depleted δ18O (cooler climate) in the 19th century appears widespread in the peninsula region and challenges our understanding of the physical relationships among moisture sources, air temperatures and snow accumulation. The complex meteorological regime in the Antarctic Peninsula region complicates meaningful interpretation of proxy indicators and results in a strong imprint of local high-frequency processes upon the larger-scale climate picture.

scholarly journals Future Temperature Extremes Will Be More Harmful: A New Critical Factor for Improved Forecasts

2019 ◽  
Vol 16 (20) ◽  
pp. 4015 ◽  
Author(s):  
Costas A. Varotsos ◽  
Yuri A. Mazei
Keyword(s):  
Climate Change ◽  
Temperature Change ◽  
Heat Waves ◽  
Extreme Temperature ◽  
Well Being ◽  
Early Warning Systems ◽  
Extreme Weather Events ◽  
Anthropogenic Activity ◽  
Extreme Temperature Events ◽  
The Past

There is increasing evidence that extreme weather events such as frequent and intense cold spells and heat waves cause unprecedented deaths and diseases in both developed and developing countries. Thus, they require extensive and immediate research to limit the risks involved. Average temperatures in Europe in June–July 2019 were the hottest ever measured and attributed to climate change. The problem, however, of a thorough study of natural climate change is the lack of experimental data from the long past, where anthropogenic activity was then very limited. Today, this problem can be successfully resolved using, inter alia, biological indicators that have provided reliable environmental information for thousands of years in the past. The present study used high-resolution quantitative reconstruction data derived from biological records of Lake Silvaplana sediments covering the period 1181–1945. The purpose of this study was to determine whether a slight temperature change in the past could trigger current or future intense temperature change or changes. Modern analytical tools were used for this purpose, which eventually showed that temperature fluctuations were persistent. That is, they exhibit long memory with scaling behavior, which means that an increase (decrease) in temperature in the past was always followed by another increase (decrease) in the future with multiple amplitudes. Therefore, the increase in the frequency, intensity, and duration of extreme temperature events due to climate change will be more pronounced than expected. This will affect human well-being and mortality more than that estimated in today’s modeling scenarios. The scaling property detected here can be used for more accurate monthly to decadal forecasting of extreme temperature events. Thus, it is possible to develop improved early warning systems that will reduce the public health risk at local, national, and international levels.

scholarly journals TOPOFIRE: A Topographically Resolved Wildfire Danger and Drought Monitoring System for the Conterminous United States

2019 ◽  
Vol 100 (9) ◽  
pp. 1607-1613 ◽  
Author(s):  
Zachary A. Holden ◽  
W. Matt Jolly ◽  
Alan Swanson ◽  
Dyer A. Warren ◽  
Kelsey Jencso ◽  
...  
Keyword(s):  
United States ◽  
Snow Water Equivalent ◽  
Wildland Fire ◽  
Early Warning Systems ◽  
The United States ◽  
Snow Accumulation ◽  
Assessment System ◽  
Shortwave Radiation ◽  
Mountainous Regions ◽  
Proactive Management

AbstractPatterns of energy and available moisture can vary over small (<1 km) distances in mountainous terrain. Information on fuel and soil moisture conditions that resolves this variation could help to inform fire and drought management decisions. Here, we describe the development of TOPOFIRE, a web-based mapping system designed to provide finely resolved information on soil water balance, drought, and wildfire danger information for the contiguous United States. We developed 8-arc-second-resolution (~250 meter) daily historical, near real-time, and 4-day forecast radiation, temperature, humidity, and snow water equivalent data and used these grids to calculate a suite of drought and wildfire danger indices. Large differences in shortwave radiation and surface air temperature with aspect contribute to greater snow accumulation and delays in melt timing on north-facing slopes, delaying fuel conditioning on shaded slopes. These datasets will help advance our understanding of the role of topography in wildland fire spread and ecological effects. Integration with national programs like the Wildland Fire Assessment System, the Wildland Fire Decision Support System, and drought early warning systems could support more proactive management of wildland fires and refine the characterization of drought in mountainous regions of the United States.

scholarly journals Saharan Hot and Dry Sirocco Winds Drive Extreme Fire Events in Mediterranean Tunisia (North Africa)

Atmosphere ◽  
2020 ◽  
Vol 11 (6) ◽  
pp. 590 ◽  
Author(s):  
Chiraz Belhadj-Khedher ◽  
Taoufik El-Melki ◽  
Florent Mouillot
Keyword(s):  
Mediterranean Basin ◽  
Heat Waves ◽  
Fire Hazard ◽  
Weather Conditions ◽  
Burned Area ◽  
Summer Drought ◽  
Climate Conditions ◽  
The Mediterranean ◽  
The Mediterranean Basin ◽  
Extreme Fire

With hot and dry summers, the Mediterranean basin is affected by recurrent fires. While drought is the major driver of the seasonal and inter-annual fire distribution in its northern and mildest climate conditions, some extreme fire events are also linked to extreme winds or heat waves. The southern part of the Mediterranean basin is located at the driest range of the Mediterranean bioclimate and is influenced by Saharan atmospheric circulations, leading to extreme hot and dry episodes, called Sirocco, and potentially acting as a major contributor to fire hazard. The recently created fire database for Tunisia was used to investigate the ±10-day pre- and post-fire timeframe of daily weather conditions associated with fire events over the 1985–2006 period. Positive anomalies in minimum and maximum temperatures, negative anomalies in air relative humidity, and a preferential south-eastern wind during fire events were identified, which were characteristic of Sirocco winds. +7 °C anomalies in air temperature and −30% in relative air humidity were the critical thresholds for the most extreme fire conditions. In addition, meteorological anomalies started two days before fire events and lasted for three days after for large fires >400 ha, which suggests that the duration of the Sirocco event is linked with fire duration and final fire size. Lastly, the yearly number of intense Sirocco events better explained the inter-annual variability of burned area over the 1950–2006 period than summer drought based on Standardized Precipitation Evaporation Index (SPEI) indices.

scholarly journals Climate since AD 1510 on Dyer Plateau, Antarctic Peninsula: evidence for recent climate change

1994 ◽  
Vol 20 ◽  
pp. 420-426 ◽  
Author(s):  
L. G. Thompson ◽  
D. A. Peel ◽  
E. Mosley-thompson ◽  
R. Mulvaney ◽  
J. Dal ◽  
...  
Keyword(s):  
19Th Century ◽  
Antarctic Peninsula ◽  
Chemical Species ◽  
Ice Cores ◽  
Warming Trend ◽  
Snow Accumulation ◽  
Annual Variations ◽  
Recent Climate ◽  
The 19Th Century ◽  
The Antarctic

A 480 year record of the oxygen-isotope ratios, dust content, chemical species and net accumulation from ice cores drilled in 1989 90 on Dyer Plateau in the Antarctic Peninsula is presented. The continuous analyses of small (sub-annual) samples reveal well-preserved annual variations in both sulfate content and δ18O, thus allowing an excellent time-scale to be established.This history reveals a recent pronounced warming in which the last two decades have been among the warmest in the last five centuries. Furthermore, unlike in East Antarctica, on Dyer Plateau conditions appear to have been fairly normal from AD 1500 to 1850 with cooler conditions from 1850 to 1930 and a warming trend dominating since 1930. Reconstructed annual layer thicknesses suggest an increase in net accumulation beginning early in the 19th century and continuing to the present. This intuitive conflict between increasing net accumulation and depleted δ18O (cooler climate) in the 19th century appears widespread in the peninsula region and challenges our understanding of the physical relationships among moisture sources, air temperatures and snow accumulation. The complex meteorological regime in the Antarctic Peninsula region complicates meaningful interpretation of proxy indicators and results in a strong imprint of local high-frequency processes upon the larger-scale climate picture.

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