Winter fog is decreasing in the fruit growing region of the Central Valley of California

Baldocchi, Dennis; Waller, Eric K.

doi:10.1002/2014gl060018

Cited by 35 publications

(30 citation statements)

References 17 publications

(25 reference statements)

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“…In a more recent study, Williams et al (2015) found that ongoing urbanization, specificly the influence of the UHI is responsible for the decrease of fog in southern California. A satellite data analysis showed that the fog frequency also decreased strongly in the California Central Valley (Baldocchi and Waller, 2014). The potential contributions of climate change, increase of air quality and agricultural practices are mentioned, however not analyzed in detail.…”

Section: Introductionmentioning

confidence: 99%

What Causes Observed Fog Trends: Air Quality or Climate Change?

Klemm

Lin

2016

Aerosol Air Qual. Res.

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Fog is a situation when the visual range, which is the horizontal visibility, is reduced to less than 1000 m near the Earth's surface by the presence of cloud droplets. Fog trend analyses are reported in the literature for hundreds of stations worldwide, the majority of which showing a considerable reduction of fog. Although fog is often associated with conditions at which cloud condensation nuclei had been activated at rH (relative humidity) > 100% and rapid growth had lead to the formation of fog droplets, this study focusses on urban air masses and conditions when rH is just below 100%. Mie scattering analysis shows that fog can form under such conditions and the reduction of the visual range is mainly caused by submicron aerosol particles which grow to diameters around 1 µm through deliquescence. The liquid water content itself is poorly correlated with the visual range. Assuming equilibrium conditions, both an increase of the air temperature and a reduction of the aerosol particle concentration lead to reductions of fog. In our example case, the increment for a temperature increase by 0.1°C had about the same effect as the reduction of aerosol concentrations by 10%. Care must be taken in projecting this result to actual conditions because the system is non-linear. However, physical evidence is presented which confirms that both climate change and an improvement of air quality are mechanisms that can contribute to the reduction of fog.

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Section: Introductionmentioning

confidence: 99%

What Causes Observed Fog Trends: Air Quality or Climate Change?

Klemm

Lin

2016

Aerosol Air Qual. Res.

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“…Aridification in the western United States has already been linked to large-scale tree dieoffs and other vegetation changes (20)(21)(22)(23). In California, where overall aridity has increased in recent decades (18) and coastal and inland fog have declined dramatically (24,25), aridification is predicted to dominate the effects of climate change on natural vegetation over the coming century (18,19,26). Although directional declines in species richness in western US grasslands in response to long-term drying trends are not yet documented, they may be expected based on evidence that grassland species richness is higher in wetter than drier years, geographical locations, and experimental treatments (27)(28)(29).…”

mentioning

confidence: 99%

Climate-driven diversity loss in a grassland community

Harrison

Gornish

Copeland

2015

Proc. Natl. Acad. Sci. U.S.A.

124

167

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Local ecological communities represent the scale at which species coexist and share resources, and at which diversity has been experimentally shown to underlie stability, productivity, invasion resistance, and other desirable community properties. Globally, community diversity shows a mixture of increases and decreases over recent decades, and these changes have relatively seldom been linked to climatic trends. In a heterogeneous California grassland, we documented declining plant diversity from 2000 to 2014 at both the local community (5 m 2 ) and landscape (27 km 2 ) scales, across multiple functional groups and soil environments. Communities became particularly poorer in native annual forbs, which are present as small seedlings in midwinter; within native annual forbs, community composition changed toward lower representation of species with a trait indicating drought intolerance (high specific leaf area). Time series models linked diversity decline to the significant decrease in midwinter precipitation. Livestock grazing history, fire, succession, N deposition, and increases in exotic species could be ruled out as contributing causes. This finding is among the first demonstrations to our knowledge of climate-driven directional loss of species diversity in ecological communities in a natural (nonexperimental) setting. Such diversity losses, which may also foreshadow larger-scale extinctions, may be especially likely in semiarid regions that are undergoing climatic trends toward higher aridity and lower productivity.L arge-scale elevational and latitudinal range shifts, altered seasonal timing, and disrupted interactions among interdependent species are well-known consequences of recent global warming, all of which are predicted to intensify in coming decades and to be accompanied by increasing rates of global extinction (1-4). Consequences of rapid climate change for the diversity of local ecological communities are far less clear; diversity might increase or decrease at any given location, depending on the particular nature of climatic changes and the potential for dispersal (5-8).

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“…Areas of complex topography are characterized by unique meteorological conditions that influence Q si : reoccurring cloud patterns such as afternoon thunderstorms [ Olyphant , ] and mountain wave clouds [ Grubišić and Billings , ], topographically driven gradients in water vapor [ Feld et al ., ], stable inversions causing persistent fog [ Underwood et al ., ; Lundquist and Cayan , ; Baldocchi and Waller , ] and trapping aerosols [ De Young et al ., ; McMeeking et al ., ], and reduced optical depths from water vapor, aerosols, and air mass due to higher elevations [ Marty et al ., ; Yang et al ., ].…”

Section: Methodsmentioning

confidence: 99%

A critical evaluation of modeled solar irradiance over California for hydrologic and land surface modeling

et al. 2017

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Studies of land surface processes in complex terrain often require estimates of meteorological variables, i.e., the incoming solar irradiance (Qsi), to force land surface models. However, estimates of Qsi are rarely evaluated within mountainous environments. We evaluated four methods of estimating Qsi: the CERES Synoptic Radiative Fluxes and Clouds (SYN) product, MTCLIM, a regional reanalysis product derived from a long‐term Weather Research and Forecast simulation, and Mountain Microclimate Simulation Model (MTCLIM). These products are evaluated over the Central Valley and Sierra Nevada mountains in California, a region with meteorology strongly impacted by complex topography. We used a spatially dense network of Qsi observations (n = 70) to characterize the spatial characteristics of Qsi uncertainty. Observation sites were grouped into five subregions, and Qsi estimates were evaluated against observations in each subregion. Large monthly biases (up to 80 W m−2) outside the observational uncertainty were found for all estimates in all subregions examined, typically reaching a maximum in the spring. We found that MTCLIM and SYN generally perform the best across all subregions. Differences between Qsi estimates were largest over the Sierra Nevada, with seasonal differences exceeding 50 W m−2. Disagreements in Qsi were especially pronounced when averaging over high‐elevation basins, with monthly differences up to 80 W m−2. Biases in estimated Qsi predominantly occurred with darker than normal conditions associated with precipitation (a proxy for cloud cover), while the presence of aerosols and water vapor was unable to explain the biases. Users of Qsi estimates in regions of complex topography, especially those estimating Qsi to force land surface models, need to be aware of this source of uncertainty.

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Winter fog is decreasing in the fruit growing region of the Central Valley of California

Cited by 35 publications

References 17 publications

What Causes Observed Fog Trends: Air Quality or Climate Change?

What Causes Observed Fog Trends: Air Quality or Climate Change?

Climate-driven diversity loss in a grassland community

A critical evaluation of modeled solar irradiance over California for hydrologic and land surface modeling

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