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1.
Climatic change threatens the future of coral reefs in the Caribbean and the important ecosystem services they provide. We used a simulation model [Combo (??COral Mortality and Bleaching Output??)] to estimate future coral cover in the part of the eastern Caribbean impacted by a massive coral bleaching event in 2005. Combo calculates impacts of future climate change on coral reefs by combining impacts from long-term changes in average sea surface temperature (SST) and ocean acidification with impacts from episodic high temperature mortality (bleaching) events. We used mortality and heat dose data from the 2005 bleaching event to select historic temperature datasets, to use as a baseline for running Combo under different future climate scenarios and sets of assumptions. Results suggest a bleak future for coral reefs in the eastern Caribbean. For three different emissions scenarios from the Intergovernmental Panel on Climate Change (IPCC; B1, A1B, and A1FI), coral cover on most Caribbean reefs is projected to drop below 5% by the year 2035, if future mortality rates are equivalent to some of those observed in the 2005 event (50%). For a scenario where corals gain an additional 1?C1.5°C of heat tolerance through a shift in the algae that live in the coral tissue, coral cover above 5% is prolonged until 2065. Additional impacts such as storms or anthropogenic damage could result in declines in coral cover even faster than those projected here. These results suggest the need to identify and preserve the locations that are likely to have a higher resiliency to bleaching to save as many remnant populations of corals as possible in the face of projected wide-spread coral loss. 相似文献
2.
This paper evaluates the global economic damage arising from the effects of climate change and associated carbon dioxide concentrations on the loss of coral reefs. We do this by first estimating the effects of sea surface temperature and carbon dioxide concentrations on coral cover. We develop a statistical relationship between coral coverage and sea surface temperature that indicates that the effects are dependent on the temperature range. For example, we find that increasing sea surface temperature causes coral coverage to decrease when sea surface temperature is higher than 26.85 °C, with the estimated reduction being 2.3% when sea surface temperature increases by 1%. In addition, we find that a 1% carbon dioxide increase induces a 0.6% reduction in global coral coverage. We also estimate the resultant loss in economic value based on a meta-analysis of the recreational and commercial value of reef coverage and a crude proportional approach for other value factors. The meta-analysis shows that the coral reef value decreases by 3.8% when coral cover falls by 1%. By combining these two steps we find that the lost value in terms of the global coral reef value under climate change scenarios ranges from US$3.95 to US$23.78 billion annually. 相似文献
3.
Cesar Villanoy Laura David Olivia Cabrera Michael Atrigenio Fernando Siringan Porfirio Aliño Maya Villaluz 《Climatic change》2012,112(2):493-505
Coral reefs and other coastal ecosystems such as seagrasses and mangroves are widely recognized to provide protection against
the devastating effects of strong waves associated with tsunamis and storms. The predicted warming climate brings to fore
the role of these ecosystems in providing protection against stronger typhoons that can result in more devastating waves of
greater amplitude. We performed a model simulation of storm generated waves on a Philippine reef, which is located along the
path of tropical storms, i.e., at least 10 typhoons on the average pass through the study site yearly. A model to simulate
wave propagation was developed using Simulating Waves Nearshore (SWAN) and DELFT3D-WAVE computer simulation software. Scenarios
involving local monsoonal wind forcing and storm conditions were simulated. In addition, as climate change may also result
to increased relative sea level, a 0.3 m and 1 m rise in sea level scenarios were also used in the wave model simulations.
Results showed that the extensive reef system in the site helped dissipate wave energy that in turn reduced wave run-up on
land. A significant reduction in wave energy was observed in both climate change, i.e., stronger wind and higher sea level,
and non-climate change scenarios. This present study was conducted in a reef whose coral cover is in excellent condition (i.e.,
50 to 80% coral cover). Estimates of coral reef growth are in the same order of magnitude as estimates of relative sea level
rise based on tide gauge and satellite altimeter data, thus it is possible that the role of reefs in attenuating wave energy
may be maintained if coral reef growth can keep up with the change in sea level. Nonetheless, to maintain reef growth, it
is imperative to manage coral reef ecosystems sustainably and to eliminate the stressors that are within human control. Minimizing
activities such as illegal and destructive blast and poison fishing methods, pollution and siltation, is crucial to minimize
the impacts of high-energy waves that may increase with climate change. 相似文献
4.
Vulnerability of coastal communities to key impacts of climate change on coral reef fisheries 总被引：1，自引：0，他引：1
J.E. Cinner T.R. McClanahan N.A.J. Graham T.M. Daw J. Maina S.M. Stead A. Wamukota K. Brown Ö. Bodin 《Global Environmental Change》2012,22(1):12-20
Coral reefs support the livelihood of millions of people especially those engaged in marine fisheries activities. Coral reefs are highly vulnerable to climate change induced stresses that have led to substantial coral mortality over large spatial scales. Such climate change impacts have the potential to lead to declines in marine fish production and compromise the livelihoods of fisheries dependent communities. Yet few studies have examined social vulnerability in the context of changes specific to coral reef ecosystems. In this paper, we examine three dimensions of vulnerability (exposure, sensitivity, and adaptive capacity) of 29 coastal communities across five western Indian Ocean countries to the impacts of coral bleaching on fishery returns. A key contribution is the development of a novel, network-based approach to examining sensitivity to changes in the fishery that incorporates linkages between fishery and non-fishery occupations. We find that key sources of vulnerability differ considerably within and between the five countries. Our approach allows the visualization of how these dimensions of vulnerability differ from site to site, providing important insights into the types of nuanced policy interventions that may help to reduce vulnerability at a specific location. To complement this, we develop framework of policy actions thought to reduce different aspects of vulnerability at varying spatial and temporal scales. Although our results are specific to reef fisheries impacts from coral bleaching, this approach provides a framework for other types of threats and different social-ecological systems more broadly. 相似文献
5.
Scott Andrew Wooldridge Terence J. Done Colette R. Thomas Iain I. Gordon Paul A. Marshall Roger N. Jones 《Climatic change》2012,112(3-4):945-961
The threats of wide-scale coral bleaching and reef demise associated with anthropogenic (global) climate change are widely known. Less well considered is the contributing role of conditions local to the reef, in particular reef water quality, in co-determining the physiological tolerance of corals to increasing sea temperatures and declining pH. Here, the modelled benefit of reduced exposure to dissolved inorganic nitrogen (DIN) in terrestrial runoff, which raises the thermal tolerance of coastal coral communities on the central Great Barrier Reef (Australia), is considered alongside alternative future warming scenarios. The simulations highlight that an 80% reduction in DIN ‘buys’ an additional ~50–60?years of reef-building capacity for No Mitigation (‘business-as-usual’) bleaching projections. Moreover, the integrated management benefits provided by: (i) local reductions of ~50% in DIN contained in river loads, and (ii) global stabilisation of atmospheric CO2 below 450?ppm can help ensure the persistence of hard-coral-dominated reefscapes beyond 2100. The simulations reinforce the message that beyond the global imperative to mitigate future atmospheric CO2 emissions there still remains the need for effective local management actions that enhance the resistance and resilience of coral reef communities to the impacts of climate change. 相似文献
6.
The UN Framework Convention on Climate Change calls for the avoidance of “dangerous anthropogenic interference with the climate
system”. Among the many plausible choices, dangerous interference with the climate system may be interpreted as anthropogenic
radiative forcing causing distinct and widespread climate change impacts such as a widespread demise of coral reefs or a disintegration
of the West Antarctic ice sheet. The geological record and numerical models suggest that limiting global warming below critical
temperature thresholds significantly reduces the likelihood of these eventualities. Here we analyze economically optimal policies
that may ensure this risk-reduction. Reducing the risk of a widespread coral reef demise implies drastic reductions in greenhouse
gas emissions within decades. Virtually unchecked greenhouse gas emissions to date (combined with the inertia of the coupled
natural and human systems) may have already committed future societies to a widespread demise of coral reefs. Policies to
reduce the risk of a West Antarctic ice sheet disintegration allow for a smoother decarbonization of the economy within a
century and may well increase consumption in the long run. 相似文献
7.
Coral reefs are highly vulnerable to the impacts of rising marine temperatures and marine heatwaves. Mitigating dangerous climate change is essential and urgent, but many reef systems are already suffering on current levels of warming. Geoengineering options are worth exploring to protect the Great Barrier Reef (GBR) from extreme warming conditions, but we contend that they require strong governance and public consultation from the outset. Australian governments are currently funding feasibility testing of three geoengineering proposals for the GBR. Each proposal involves manipulating ocean or atmospheric conditions to lower water temperatures and thereby reduce the threat of mass coral bleaching events. Innovative strategies to protect the GBR and field testing of these is essential, but current laws do not guarantee robust governance for field testing of these technologies. Nor do they provide the foundation for a more coherent national policy on climate intervention technologies more generally. Responsible governance frameworks, including detailed risk assessment and early public consultation, are necessary for geoengineering research to build legitimacy and promote scientific progress.
Key policy insights
Marine heatwaves pose a serious threat to coral reefs, including Australia’s iconic Great Barrier Reef.
Australian governments have recognized the threats of warming waters, and are funding research of geoengineering options for the Great Barrier Reef.
The limited earlier field testing of geoengineering demonstrates the need for specific governance to manage risks, build legitimacy and maintain public support.
Australia requires a framework to govern geoengineering research and development before deployment of such technologies.
8.
A dramatic escalation of extreme climate events is challenging the capacity of environmental governance regimes to sustain and improve ecosystem outcomes. It has been argued that actors within adaptive governance regimes can help to steer environmental systems toward sustainability in times of crisis. Yet there is little empirical evidence of how acute climate crises are navigated by actors operating within adaptive governance regimes, and the factors that influence their responses. Here, we qualitatively assessed the actions key governance actors took in response to back-to-back mass coral bleaching – an extreme climate event – of the Great Barrier Reef in 2016 and 2017, and explored their perceptions of barriers and catalysts to these responses. This research was, in part, a product of collaboration and knowledge co-production with Great Barrier Reef governance actors aimed at improving responses to climate crises in the region. We found five major categories of activity that actors engaged with in the wake of recurrent mass coral bleaching: assessing the scale and extent of bleaching, sharing information, communicating bleaching to the public, building local resilience, and addressing global threats. These actions were both catalyzed and hindered by a range of factors that fall within different domains of adaptive capacity; such as assets, social organization, and agency. We discuss the implications of our findings as they relate to existing research on adaptive capacity and adaptive governance. We conclude by coalescing insights from our interviews and a participant engagement process to highlight four key ways in which the ability of governance actors, and the Great Barrier Reef governance regime more broadly, can be better prepared for, and more effectively respond to extreme climate events. Our research provides empirical insight into how crises are experienced by governance actors in a large-scale environmental system, potentially providing lessons for similar systems across the globe. 相似文献
9.
The twin crisis of biodiversity loss and climate change make it urgent to find ways of restoring natural ecosystems, including coral reefs. Methods for coral reef restoration are rapidly advancing, bringing with them a range of potential risks and opportunities. Attention to public engagement in the governance of such activities therefore becomes critical. This research examines public attitudinal and behavioral engagement in ‘traditional’ coral restoration projects in the Great Barrier Reef World Heritage Area (i.e. coral gardening at relatively small scales). Grounded on dual-process decision-making and trust theories, rational factors (i.e., perceived benefits), emotions (i.e., hope and guilt) and trust are conceptually three main determinants of public engagement in ecological restoration. We used a mixed-method approach, including 63 individual interviews and a follow-up survey with 1585 participants, to clarify the roles of these psychological factors in motivating public engagement in current coral restoration projects. Trust was found to be the most important factor influencing public acceptance (i.e., attitudinal engagement) of coral restoration, while the emotion of guilt was the most influential factor affecting public support (i.e., behavioral engagement). Therefore, when advocating for conservation projects, different campaigns could be implemented with: (1) positive messages of hope and trust to gain public acceptance for government-funded restoration projects and (2) messages highlighting individual responsibility to motivate behavioral support to scale up restoration projects. 相似文献
10.
Lester Kwiatkowski Paul R. Halloran Peter J. Mumby David B. Stephenson 《Climate Dynamics》2014,43(5-6):1483-1496
Earth system models (ESMs) provide high resolution simulations of variables such as sea surface temperature (SST) that are often used in off-line biological impact models. Coral reef modellers have used such model outputs extensively to project both regional and global changes to coral growth and bleaching frequency. We assess model skill at capturing sub-regional climatologies and patterns of historical warming. This study uses an established wavelet-based spatial comparison technique to assess the skill of the coupled model intercomparison project phase 5 models to capture spatial SST patterns in coral regions. We show that models typically have medium to high skill at capturing climatological spatial patterns of SSTs within key coral regions, with model skill typically improving at larger spatial scales (≥4°). However models have much lower skill at modelling historical warming patters and are shown to often perform no better than chance at regional scales (e.g. Southeast Asian) and worse than chance at finer scales (<8°). Our findings suggest that output from current generation ESMs is not yet suitable for making sub-regional projections of change in coral bleaching frequency and other marine processes linked to SST warming. 相似文献
11.
使用UVic地球系统气候模式,在4种CO2典型浓度路径（RCP2.6、RCP4.5、RCP6.0、RCP8.5）情景下,对1800-2300年海洋环境变化及珊瑚礁周围海水环境进行模拟分析。结果表明,海洋将继续吸收大量碳,从RCP2.6到RCP8.5情景,海表温度将在21世纪末上升1.1～2.8 K,pH值将下降0.14～0.42,[CO32- ]将减少20%～51%。珊瑚礁周围环境的文石饱和度（W）下降迅速。在工业革命前,99%的浅水珊瑚处于W>3.5的外环境中,87%的深水珊瑚处于W>1的海域。在21世纪末,除了RCP2.6,其他情景下均仅剩不到1%的浅水珊瑚还能被W>3.5的水域包围。在RCP8.5情景下,21世纪末全球平均文石饱和线将从工业革命前的1138 m水深提升到308 m水深,使得73%的冷水珊瑚暴露在不饱和水域,而2300年这一比例将超过95%。 相似文献
12.
Mellissa C. MacKellar Hamish A. McGowan Stuart R. Phinn Joshua S. Soderholm 《Boundary-Layer Meteorology》2013,146(2):319-340
Over warm, shallow coral reefs the surface radiation and energy fluxes differ from those of the open ocean and result in modification to the marine atmospheric boundary layer via the development of convective internal boundary layers. The complex interrelationships between the surface energy balance and boundary-layer characteristics influence local weather (wind, temperature, humidity) and hydrodynamics (water temperature and currents), as well as larger scale processes, including cloud field properties and precipitation. The nature of these inter-relationships has not been accurately described for coral reef environments. This study presents the first measurements of the surface energy balance, radiation budget and boundary layer thermodynamics made over a coral reef using an eddy-covariance system and radiosonde aerological profiling of the lower atmosphere. Results show that changes in surface properties and the associated energetics across the ocean-reef boundary resulted in modification to the marine atmospheric boundary layer during the Austral winter and summer. Internal convective boundary layers developed within the marine atmospheric boundary layer over the reef and were found to be deeper in the summer, yet more unstable during the winter when cold and drier flow from the mainland enhances heat and moisture fluxes to the atmosphere. A mixed layer was identified in the marine atmospheric boundary layer varying from 375 to 1,200 m above the surface, and was deeper during the summer, particularly under stable anticyclonic conditions. Significant cloud cover and at times rain resulted in the development of a stable stratified atmosphere over the reef. Our findings show that, for Heron Reef, a lagoonal platform reef, there was a horizontal discontinuity in surface energy fluxes across the ocean-reef boundary, which modified the marine atmospheric boundary layer. 相似文献
13.
Interdecadal Change of the Relationship Between the Tropical Indian Ocean Dipole Mode and the Summer Climate Anomaly in China 总被引：2，自引：0，他引：2 
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下载免费PDF全文 ZHAO Shanshan ZHOU Tianjun YANG Xiuqun ZHU Yimin TAN Yanke SUN Xuguang 《Acta Meteorologica Sinica》2011,25(2):129-141
The interdecadal change of the relationship between the tropical Indian Ocean dipole(IOD) mode and the summer climate anomaly in China is investigated by using monthly precipitation and temperature records at 210 stations in China and the NCEP/NCAR reanalysis data for 1957-2005.The results indicate that along with the interdecadal shift in the large-scale general circulation around the late 1970s,the relationship between the IOD mode and the summer climate anomaly in some regions of China has significantly changed.Before the late 1970s,a developing IOD event is associated with an enhanced East Asian summer monsoon,which tends to decrease summer precipitation and increase summer temperature in South China;while after the late 1970s,it is associated with a weakened East Asian summer monsoon,which tends to increase(decrease) precipitation and decrease(increase) temperature in the south(north) of the Yangtze River.During the next summer,following a positive IOD event,precipitation is increased in most of China before the late 1970s,while it is decreased(increased) south(north) of the Yangtze River after the late 1970s.There is no significant correlation between the IOD and surface air temperature anomaly in most of China in the next summer before the late 1970s;however,the IOD tends to increase the next summer temperature south of the Yellow River after the late 1970s. 相似文献
14.
Jonathan Rougier 《Climatic change》2007,81(3-4):247-264
This paper describes an approach to computing probabilistic assessments of future climate, using a climate model. It clarifies
the nature of probability in this context, and illustrates the kinds of judgements that must be made in order for such a prediction
to be consistent with the probability calculus. The climate model is seen as a tool for making probabilistic statements about
climate itself, necessarily involving an assessment of the model’s imperfections. A climate event, such as a 2^C increase in global mean temperature, is identified with a region of ‘climate-space’, and the ensemble of model evaluations
is used within a numerical integration designed to estimate the probability assigned to that region. 相似文献
15.
Wyoming provides more fossil fuels to the remainder of the United States than any other state or country, and its citizens
remain skeptical of anthropogenic influences on their climate. However, much of the state including Yellowstone National Park
and the headwaters of several major river systems, may have already been affected by rising temperatures. This paper examines
the historic climate record from Wyoming in the context of ∼14,000-year temperature reconstructions based on fossil pollen
data. The analysis shows that 24 of 30 U.S. Historical Climatology Network records from the state show an increase in the
frequency of unusually warm years since 1978. Statewide temperatures have included 15 years (50%) from 1978 to 2007 that were
greater than 1σ above the mean annual temperature for 1895–1978. The frequent warm years coincide with a reduction in the
frequency of extremely low (<−20°C) January temperatures, and are not well explained by factors such as solar irradiance and
the Pacific Decadal Oscillation. Linear regressions require inclusion of atmospheric greenhouse gas concentrations to explain
the multi-decadal temperature trends. The observed warming is large in Yellowstone National Park where 21 years (70%) from
1978 to 2007 were greater than 1σ above the 1895–1978 mean; the deviation from the mean (>1°C) is greater than any time in
the past 6,000 years. Recent temperatures have become as high as those experienced from 11,000 to 6,000 years ago when summer
insolation was >6% higher than today and when regional ecosystems experienced frequent severe disturbances. 相似文献
16.
This paper discusses methodological issues relevant to the calculation of historical responsibility of countries for climate
change (‘The Brazilian Proposal’). Using a simple representation of the climate system, the paper compares contributions to
climate change using different indicators: current radiative forcing, current GWP-weighted emissions, radiative forcing from
increased concentrations, cumulative GWP-weighted emissions, global-average surface-air temperature increase and two new indicators:
weighted concentrations (analogue to GWP-weighted emissions) and integrated temperature increase. Only the last two indicators
are at the same time ‘backward looking’ (take into account historical emissions), ‘backward discounting’ (early emissions
weigh less, depending on the decay in the atmosphere) and ‘forward looking’ (future effects of the emissions are considered)
and are comparable for all gases. Cumulative GWP-weighted emissions are simple to calculate but are not ‘backward discounting’.
‘Radiative forcing’ and ‘temperature increase’ are not ‘forward looking’. ‘Temperature increase’ discounts the emissions of
the last decade due to the slow response of the climate system. It therefore gives low weight to regions that have recently
significantly increased emissions. Results of the five different indicators are quite similar for large groups (but possibly
not for individual countries): industrialized countries contributed around 60% to today’s climate change, developing countries
around 40% (using the available data for fossil, industrial and forestry CO2, CH4 and N2O). The paper further argues including non-linearities of the climate system or using a simplified linear system is a political
choice. The paper also notes that results of contributions to climate change need to be interpreted with care: Countries that
developed early benefited economically, but have high historical emission, and countries developing at a later period can
profit from developments in other countries and are therefore likely to have a lower contribution to climate change. 相似文献
17.
Reconstructing the temporal and spatial climate development on a seasonal basis during the last few centuries, including the
‘Little Ice Age’, may help us better understand modern-day interplay between natural and anthropogenic climate variability.
The conventional view of the climate development during the last millennium has been that it followed a sequence of a Medieval
Warm Period, a cool ‘Little Ice Age’ and a warming during the later part of the 19th century and in particular during the
late 20th/early 21st centuries. However, recent research has challenged this rather simple sequence of climate development.
Up to the present, it has been considered most likely that the ‘Little Ice Age’ glacial expansion in western Scandinavia was
due to lower summer temperatures. Data presented here, however, indicate that the main cause of the early 18th century glacial
advance in western Scandinavia was mild and humid winters associated with increased precipitation and high snowfall on the
glaciers. 相似文献
18.
Susan Hanson Robert Nicholls N. Ranger S. Hallegatte J. Corfee-Morlot C. Herweijer J. Chateau 《Climatic change》2011,104(1):89-111
This paper presents a first estimate of the exposure of the world’s large port cities (population exceeding one million inhabitants
in 2005) to coastal flooding due to sea-level rise and storm surge now and in the 2070s, taking into account scenarios of
socio-economic and climate changes. The analysis suggests that about 40 million people (0.6% of the global population or roughly
1 in 10 of the total port city population in the cities considered) are currently exposed to a 1 in 100 year coastal flood
event. For assets, the total value exposed in 2005 across all cities considered is estimated to be US$3,000 billion; corresponding
to around 5% of global GDP in 2005 (both measured in international USD) with USA, Japan and the Netherlands being the countries
with the highest values. By the 2070s, total population exposed could grow more than threefold due to the combined effects
of sea-level rise, subsidence, population growth and urbanisation with asset exposure increasing to more than ten times current
levels or approximately 9% of projected global GDP in this period. On the global-scale, population growth, socio-economic
growth and urbanization are the most important drivers of the overall increase in exposure particularly in developing countries,
as low-lying areas are urbanized. Climate change and subsidence can significantly exacerbate this increase in exposure. Exposure
is concentrated in a few cities: collectively Asia dominates population exposure now and in the future and also dominates
asset exposure by the 2070s. Importantly, even if the environmental or socio-economic changes were smaller than assumed here
the underlying trends would remain. This research shows the high potential benefits from risk-reduction planning and policies
at the city scale to address the issues raised by the possible growth in exposure. 相似文献
19.
The aim of this paper is to re-examine and quantify a hypothesis first put forward by J. Bjerknes concerning the anomalous
coldness during the AD 1790–1820 period in western Europe. Central to Bjerknes’ hypothesis is an anomalous interaction between
ocean and atmosphere studied here using an ocean-atmosphere coupled climate model of intermediate complexity. A reconstruction
of the sea-level pressure pattern over the North Atlantic sector averaged over the period 1790–1820 is assimilated in this
model, using a recently developed technique which has not been applied to paleoclimatic modelling before. This technique ensures
that averaged over the simulation the reconstructed pattern is retrieved whilst leaving atmospheric and climatic variability to develop
freely. In accordance with Bjerknes’ hypothesis, the model results show anomalous southward advection of polar waters into
the northeastern North Atlantic in the winter season, lowering the sea-surface temperatures (SSTs) there with 0.3–1.0°C. This
SST anomaly is persistent into the summer season. A decrease in western European winter surface air temperatures is found
which can be related almost completely to advection of cold polar air. The decrease in summer surface air temperatures is
related to a combination of low SSTs and anomalous atmospheric circulation. The modelled winter and summer temperatures in
Europe compare favourably with reconstructed temperatures. Enhanced baroclinicity at the Atlantic seaboard and over Baffin
Island is observed along with more variability in the position of the North Atlantic storm tracks. The zone of peak winter
storm frequency is drawn to the European mid-latitudes.
In the original article (Climate Dynamics (2005) 24: 355-371; ) figures 4, 7, 8, 10, 11 and 13 were unfortunately incorrect. The correct version is shown here. 相似文献
20.
The atmospheric conditions that lead to strong offshore surface winds in Southern California, commonly referred to as Santa
Ana winds, are investigated using the North American Regional Reanalysis and a 12-year, 6-km resolution regional climate simulation
of Southern California. We first construct an index to characterize Santa Ana events based on offshore wind strength. This
index is then used to identify the average synoptic conditions associated with Santa Ana events—a high pressure anomaly over
the Great Basin. This pressure anomaly causes offshore geostrophic winds roughly perpendicular to the region’s mountain ranges,
which in turn cause surface flow as the offshore momentum is transferred to the surface. We find, however, that there are
large variations in the synoptic conditions during Santa Ana conditions, and that there are many days with strong offshore
flow and weak synoptic forcing. This is due to local thermodynamic forcing that also causes strong offshore surface flow:
a large temperature gradient between the cold desert surface and the warm ocean air at the same altitude creates an offshore
pressure gradient at that altitude, in turn causing katabatic-like offshore flow in a thin layer near the surface. We quantify
the contribution of “synoptic” and “local thermodynamic” mechanisms using a bivariate linear regression model, and find that,
unless synoptic conditions force strongly onshore winds, the local thermodynamic forcing is the primary control on Santa Ana
variability. 相似文献