The regionally varying effects of forests on cloud cover based on satellite observations

2020 ◽  
Author(s):  
Yan Li ◽  
Ru Xu ◽  
Adriaan J. Teuling ◽  
Zhao Lei
Keyword(s):  
Boreal Forests ◽  
Cloud Cover ◽  
Forest Cover ◽  
Water Cycle ◽  
Global Climate ◽  
Global Scale ◽  
Boreal Summer ◽  
Forest Cover Change ◽  
Cloud Data ◽  
The Impact

<p>Forests cover changes impact regional and global climate by altering surface roughness, albedo, and evapotranspiration. While previous research mainly focused on the impact on temperature, there has been evidence of cloud enhancement over forests at the regional level. However, how forests affect cloud cover at a global scale is unclear. In this paper, we utilized long-term cloud data from MODIS in junction with other satellite data sources to investigate the effects of forests on cloud cover in boreal summer months across the globe. Results show that forests either increase or decrease cloud cover depending on the region and such effect exhibits considerable spatial heterogeneity. We found that forests in the southern edge of tropical Amazon decreased cloud cover as much as 6%. In contrast, forests can significantly increase cloud coverage in southern part of China in temperate region. Furthermore, the cloud increase was also observed in boreal forests but with a smaller magnitude than temperate forests. Our study provides new evidence for understanding the impact of forest cover change on cloud and water cycle.</p>

scholarly journals The Hydrologic Feedback Pathway for Land–Climate Coupling

2006 ◽  
Vol 7 (5) ◽  
pp. 857-867 ◽  
Author(s):  
Paul A. Dirmeyer
Keyword(s):  
Land Surface ◽  
Climate Model ◽  
Water Cycle ◽  
Initial Conditions ◽  
Global Climate ◽  
Global Climate Model ◽  
Signal Transmission ◽  
Hydrologic Cycle ◽  
Boreal Summer ◽  
The Impact

Abstract The impact of improvements in land surface initialization and specification of observed rainfall in global climate model simulations of boreal summer are examined to determine how the changes propagate around the hydrologic cycle in the coupled land–atmosphere system. On the global scale, about 70% of any imparted signal in the hydrologic cycle is lost in the transition from atmosphere to land, and 70% of the remaining signal is lost from land to atmosphere. This means that globally, less than 10% of the signal of any change survives the complete circuit of the hydrologic cycle in this model. Regionally, there is a great deal of variability. Specification of observed precipitation to the land component of the climate model strongly communicates its signal to soil wetness in rainy regions, but predictive skill in evapotranspiration arises primarily in dry regions. A maximum in signal transmission to model precipitation exists in between, peaking where mean rainfall rates are 1.5–2 mm day−1. It appears that the nature of the climate system inherently limits to these regions the potential impact on prediction of improvements in the ability of models to simulate the water cycle. Land initial conditions impart a weaker signal on the system than replacement of precipitation, so a weaker response is realized in the system, focused mainly in dry regions.

scholarly journals Fully Automated Light Precipitation Detection from MPLNET and EARLINET Network Lidar Measurements

2020 ◽  
Vol 237 ◽  
pp. 05006
Author(s):  
Simone Lolli ◽  
Gemine Vivone ◽  
Ellsworth J. Welton ◽  
Jasper R. Lewis ◽  
James R. Campbell ◽  
...  
Keyword(s):  
Climate Models ◽  
Hydrological Cycle ◽  
Water Cycle ◽  
Global Climate ◽  
Global Scale ◽  
Global Climate Models ◽  
Morphological Filters ◽  
Lidar Measurements ◽  
Life On Earth ◽  
Light Precipitation

The water cycle strongly influence life on Earth and precipitation especially modifies the atmospheric column thermodynamics through the evaporation process and serving as a proxy for latent heat modulation. For this reason, a correct light precipitation parameterization at global scale, it is of fundamental importance, bedsides improving our understanding of the hydrological cycle, to reduce the associated uncertainty of the global climate models to correctly forecast future scenarios. In this context we developed a full automatic algorithm based on morphological filters that, once operational, will make available a new rain product for the NASA Micropulse Lidar Network (MPLNET) and the European Aerosol Research Lidar Network (EARLINET) in the frame of WMO GALION Project

scholarly journals Potential impact of aerosols on convective clouds revealed by Himawari-8 observations over different terrain types in eastern China

2021 ◽  
Vol 21 (8) ◽  
pp. 6199-6220
Author(s):  
Tianmeng Chen ◽  
Zhanqing Li ◽  
Ralph A. Kahn ◽  
Chuanfeng Zhao ◽  
Daniel Rosenfeld ◽  
...  
Keyword(s):  
Water Cycle ◽  
Eastern China ◽  
Convective Cloud ◽  
Northern China ◽  
Cloud Data ◽  
Convective Clouds ◽  
Cloud Properties ◽  
Cloud Development ◽  
Potential Impact ◽  
The Impact

Abstract. Convective clouds are common and play a major role in Earth's water cycle and energy balance; they may even develop into storms and cause severe rainfall events. To understand the convective cloud development process, this study investigates the impact of aerosols on convective clouds by considering the influence of both topography and diurnal variation in radiation. By combining texture analysis, clustering, and thresholding methods, we identify all convective clouds in two warm seasons (May–September, 2016/17) in eastern China based on Himawari-8 Level 1 data. Having large diurnally resolved cloud data together with surface meteorological and environmental measurements, we investigate convective cloud properties and their variation, stratified by elevation and diurnal change. We then analyze the potential impact of aerosol on convective clouds under different meteorological conditions and topographies. In general, convective clouds tend to occur preferentially under polluted conditions in the morning, which reverses in the afternoon. Convective cloud fraction first increases then decreases with aerosol loading, which may contribute to this phenomenon. Topography and diurnal meteorological variations may affect the strength of aerosol microphysical and radiative effects. Updraft is always stronger along the windward slopes of mountains and plateaus, especially in northern China. The prevailing southerly wind near the foothills of mountains and plateaus is likely to contribute to this windward strengthening of updraft and to bring more pollutant into the mountains, thereby strengthening the microphysical effect, invigorating convective clouds. By comparison, over plain, aerosols decrease surface heating and suppress convection by blocking solar radiation reaching the surface.

Remote Sensing

2015 ◽  
Author(s):  
Frank D. Eckardt
Keyword(s):  
Remote Sensing ◽  
Real Time ◽  
Vegetation Index ◽  
Forest Cover ◽  
Normalized Difference Vegetation Index ◽  
Laser Pulses ◽  
Global Scale ◽  
Dynamic Topography ◽  
Forest Cover Change ◽  
Atmospheric Remote Sensing

This article on remote sensing or earth observation focuses on mapping and monitoring systems that produce global-scale data sets which are easily accessible to the wider public. It makes particular reference to low-earth-orbiting remote sensing platforms and sensors and associated image archives such as provided by the Landsat and Moderate-Resolution Imaging Spectroradiometer (MODIS) programs. It also draws attention to handheld space photography, synthetic aperture radar (SAR), and the high-spatial-resolution capability obtained from the commercial remote sensing sector. This entry examines applications that are of global interest and are facilitated through image and data portals. Particular emphasis is placed on products such as the normalized difference vegetation index, real-time fire mapping, forest cover change, geomorphology, and global elevation data as well as actual true- and false-color imagery. All of these can be readily imported as shape or raster files into a Geographic Information System (GIS). Key papers dealing with the global monitoring of the biosphere, dynamic topography, and gravity are being cited. Special emphasis is placed on current capabilities in monitoring recent and ongoing changes in the tropics as well as Arctic and Antarctic environment. Numerous remote sensing systems capture the state and dynamics of rainforests, ice caps, glaciers, and shelf and sea ice, some of which are available in near-real-time trend analysis. Not all sensors produce images; some measure passive microwaves, send laser pulses, or detect small fluctuations in gravitational attraction. Nevertheless, all instruments measure changes in earth’s surface state, indicative of seasonal cycles and long-term trends as well as human impact. This article also makes reference to historic developments, social benefits, and ethical considerations in remote sensing as well as the modern role of aerial photography and airborne platforms. Most people will never get to see a satellite or its instruments, they might not even get to see the available data or imagery, but these systems are directly informing the masses or indirectly shaping the perception of a changing and dynamic world. Future revisions to this article will consider oceanographic and atmospheric remote sensing capabilities.

scholarly journals Intergyre Salt Transport in the Climate Warming Response

2020 ◽  
Vol 50 (1) ◽  
pp. 255-268
Author(s):  
Samuel J. Levang ◽  
Raymond W. Schmitt
Keyword(s):  
Ocean Circulation ◽  
Climate Warming ◽  
Climate Model ◽  
Water Cycle ◽  
Global Climate ◽  
Salt Transport ◽  
Ocean Dynamics ◽  
Subpolar Gyre ◽  
Salinity Response ◽  
The Impact

ABSTRACTRegional connectivity is important to the global climate salinity response, particularly because salinity anomalies do not have a damping feedback with atmospheric freshwater fluxes and may therefore be advected over long distances by ocean circulation, resulting in nonlocal influences. Climate model intercomparison experiments such as CMIP5 exhibit large uncertainty in some aspects of the salinity response, hypothesized here to be a result of ocean dynamics. We use two types of Lagrangian particle tracking experiments to investigate pathways of exchange for salinity anomalies. The first uses forward trajectories to estimate average transport time scales between water cycle regimes. The second uses reverse trajectories and a freshwater accumulation method to quantitatively identify remote influences in the salinity response. Additionally, we compare velocity fields with both resolved and parameterized eddies to understand the impact of eddy stirring on intergyre exchange. These experiments show that surface anomalies are readily exchanged within the ocean gyres by the mean circulation, but intergyre exchange is slower and largely eddy driven. These dynamics are used to analyze the North Atlantic salinity response to climate warming and water cycle intensification, where the system is broadly forced with fresh surface anomalies in the subpolar gyre and salty surface anomalies in the subtropical gyres. Under these competing forcings, strong intergyre eddy fluxes carry anomalously salty subtropical water into the subpolar gyre which balances out much of the local freshwater input.

scholarly journals Rainfall anomalies are a significant driver of cropland expansion

2020 ◽  
Vol 117 (19) ◽  
pp. 10225-10233 ◽  
Author(s):  
Esha Zaveri ◽  
Jason Russ ◽  
Richard Damania
Keyword(s):  
Developing Countries ◽  
Forest Cover ◽  
Global Scale ◽  
Alternative Measure ◽  
Productivity Shocks ◽  
Small Holder Farmers ◽  
Rainfall Anomalies ◽  
The Impact ◽  
The Relationship ◽  
Grid Level

Rainfall anomalies have long occupied center stage in policy discussions, and understanding their impacts on agricultural production has become more important as climate change intensifies. However, the global scale of rainfall-induced productivity shocks on changes in cropland is yet to be quantified. Here we identify how rainfall anomalies impact observed patterns of cropped areas at a global scale by leveraging locally determined unexpected variations in rainfall. Employing disaggregated panel data at the grid level, we find that repeated dry anomalies lead to an increase in cropland expansion in developing countries. No discernible effects are detected from repeated wet events. That these effects are confined to developing countries, which are often dominated by small-holder farmers, implies that they may be in response to reduced yields. The estimates suggest that overall, in developing countries, dry anomalies account for ∼9% of the rate of cropland expansion over the past two decades. We perform several tests to check for consistency and robustness of this relationship. First, using forest cover as an alternative measure, we find comparable reductions in forest cover in the same regions where cropland expands due to repeated dry anomalies. Second, we test the relationship in regions where yields are buffered from rainfall anomalies by irrigation infrastructure and find that the impact on cropland expansion is mitigated, providing further support for our results. Since cropland expansion is a significant driver of deforestation, these results have important implications for forest loss and environmental services.

The NASA Atmospheric Tomography Mission: A Global-Scale Survey of Composition, Reactivity, and Transport in the Remote Atmosphere

2020 ◽  
Author(s):  
Chelsea Thompson ◽  
Keyword(s):  
Human Activity ◽  
Climate Models ◽  
Technological Development ◽  
Global Climate ◽  
Global Scale ◽  
Chemical Production ◽  
New Findings ◽  
Chemical Destruction ◽  
Research Aircraft ◽  
The Impact

<p>     The last seventy years have witnessed a marked acceleration of the impact of human activity impacting the planet due to the combination of rapid population growth, increased consumption of resources, and technological development. Nearly the entire human population occupies an astonishingly small percentage of the Earth’s surface, yet the imprint of human activity is being recorded in global climate and is perturbing the chemistry and composition of the most remote stretches of the atmosphere. These remote regions are exceptionally important for global air quality and climate (accounting on average for 75% of global CH<sub>4</sub> removal, 59% of chemical production of O<sub>3</sub>, and 68% of chemical destruction of O<sub>3</sub>), yet the paucity of observations over the remote oceans have limited our understanding of these fundamental processes and their sensitivity to increased human perturbation.</p><p>     The NASA Atmospheric Tomography Mission (ATom) was designed to address these gaps in our understanding of chemical composition, reactivity, and transport through a combination of extensive measurements and photochemical modeling, and to provide much needed observational data from the remote regions of the atmosphere to provide rigorous tests that will lead to improvements in our global chemistry-climate models and to validate remote sensing retrievals. From 2016-2018, ATom utilized the fully instrumented NASA DC-8 research aircraft to collect an unprecedented suite of measurements of trace gases, aerosols, and key radical species from the remote troposphere and lower stratosphere.  Four complete pole-to-pole global circuits (one in each season) were conducted by performing near-continuous vertical profiles between 0.2 – 14 km altitude along meridional transects of the Pacific and Atlantic Ocean Basins. The data provided by this project have already led to several significant new findings, with many more on the horizon as research teams continue to uncover the full value of this dataset. In this talk, we will provide an overview of the ATom mission and discuss some of the major outcomes and new findings that have resulted from this project to date.</p>

scholarly journals Regional Influence of Wildfires on Aerosol Chemistry in the Western US and Insights into Atmospheric Aging of Biomass Burning Organic Aerosol

2016 ◽  
Author(s):  
Shan Zhou ◽  
Sonya Collier ◽  
Daniel A. Jaffe ◽  
Nicole L. Briggs ◽  
Jonathan Hee ◽  
...  
Keyword(s):  
Pacific Northwest ◽  
Biomass Burning ◽  
Atmospheric Aerosols ◽  
Global Climate ◽  
Organic Aerosol ◽  
The United States ◽  
Global Scale ◽  
Aerosol Composition ◽  
Photo Oxidation ◽  
The Impact

Abstract. Biomass burning (BB) is one of the most important contributors to atmospheric aerosols on a global scale and wildfires are a large source of emissions that impact regional air quality and global climate. As part of the Biomass Burning Observation Project (BBOP) field campaign in summer 2013, we deployed a High Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-AMS) coupled with a thermodenuder at the Mt. Bachelor Observatory (MBO, ~ 2.8 km above sea level) to characterize the impact of wildfire emissions on aerosol loading and properties in the Pacific Northwest region of the United States. MBO represents a remote background site in the western U.S. and it is frequently influenced by transported wildfire plumes during summer. Very clean conditions were observed at this site during periods without BB influence where the 5-min average (±1σ) concentration of non-refractory submicron aerosols (NR-PM1) was 3.7 ± 4.2 μg m−3. Aerosol concentration increased substantially (reaching up to 210 µg m−3 of NR-PM1) for periods impacted by transported BB plumes and aerosol composition was overwhelmingly organic. Based on Positive Matrix Factorization (PMF) of the HR-AMS data, three types of BB organic aerosol (BBOA) were identified, including a fresh, semivolatile BBOA-1 (O/C = 0.35; 20 % of OA mass) that correlated well with ammonium nitrate, an intermediately oxidized BBOA-2 (O/C = 0.60; 17 % of OA mass), and a highly oxidized BBOA-3 (O/C = 1.06; 31 % of OA mass) that showed very low volatility with only ~ 40 % mass loss at 200 °C. The remaining 32 % of the organic aerosol (OA) mass was attributed to a boundary layer (BL) OOA (BL-OOA; O/C = 0.69) representing OA influenced by BL dynamics and a low-volatility oxygenated OA (LV-OOA; O/C = 1.09) representing regional free troposphere aerosol. The mass spectrum of BBOA-3 resembled that of LV-OOA and had negligible contributions from the HR-AMS BB tracer ions – C2H4O2+ (m/z = 60.021) and C3H5O2+ (m/z = 73.029). This finding highlights the possibility that the influence of BB emission could be underestimated in regional air masses where highly oxidized BBOA (e.g. BBOA-3) might be a significant aerosol component. We also examined OA chemical evolution for persistent BB plume events originating from a single fire source and found that longer solar radiation led to higher mass fraction of the chemically aged BBOA-2 and BBOA-3 and more oxidized aerosol. However, an analysis of the enhancement ratios of OA relative to CO (ΔOA/ΔCO) showed little difference between BB plumes transported primarily at night versus during the day, despite evidence of substantial chemical transformation in OA induced by photo-oxidation. These results indicate negligible net OA production with photo-oxidation for wildfire plumes observed in this study, for which a possible reason is that SOA formation was almost entirely balanced by BBOA volatilization.

scholarly journals Object-Based Classification of Forest Disturbance Types in the Conterminous United States

2019 ◽  
Vol 11 (5) ◽  
pp. 477 ◽  
Author(s):  
Lian-Zhi Huo ◽  
Luigi Boschetti ◽  
Aaron Sparks
Keyword(s):  
United States ◽  
Forest Cover ◽  
Forest Disturbance ◽  
Global Scale ◽  
Management Policy ◽  
Forest Loss ◽  
Forest Cover Change ◽  
Forest Change ◽  
Goods And Services ◽  
Moderate Resolution Imaging Spectroradiometer

Forest ecosystems provide critical ecosystem goods and services, and any disturbance-induced changes can have cascading impacts on natural processes and human socioeconomic systems. Forest disturbance frequency, intensity, and spatial and temporal scale can be altered by changes in climate and human activity, but without baseline forest disturbance data, it is impossible to quantify the magnitude and extent of these changes. Methodologies for quantifying forest cover change have been developed at the regional-to-global scale via several approaches that utilize data from high (e.g., IKONOS, Quickbird), moderate (e.g., Landsat) and coarse (e.g., Moderate Resolution Imaging Spectroradiometer (MODIS)) spatial resolution satellite imagery. While detection and quantification of forest cover change is an important first step, attribution of disturbance type is critical missing information for establishing baseline data and effective land management policy. The objective here was to prototype and test a semi-automated methodology for characterizing high-magnitude (>50% forest cover loss) forest disturbance agents (stress, fire, stem removal) across the conterminous United States (CONUS) from 2003–2011 using the existing University of Maryland Landsat-based Global Forest Change Product and Web-Enabled Landsat Data (WELD). The Forest Cover Change maps were segmented into objects based on temporal and spatial adjacency, and object-level spectral metrics were calculated based on WELD reflectance time series. A training set of objects with known disturbance type was developed via high-resolution imagery and expert interpretation, ingested into a Random Forest classifier, which was then used to attribute disturbance type to all 15,179,430 forest loss objects across CONUS. Accuracy assessments of the resulting classification was conducted with an independent dataset consisting of 4156 forest loss objects. Overall accuracy was 88.1%, with the highest omission and commission errors observed for fire (32.8%) and stress (31.9%) disturbances, respectively. Of the total 172,686 km2 of forest loss, 83.75% was attributed to stem removal, 10.92% to fire and 5.33% to stress. The semi-automated approach described in this paper provides a promising framework for the systematic characterization and monitoring of forest disturbance regimes.

scholarly journals The Impact of Different Absolute Solar Irradiance Values on Current Climate Model Simulations

2014 ◽  
Vol 27 (3) ◽  
pp. 1100-1120 ◽  
Author(s):  
David H. Rind ◽  
Judith L. Lean ◽  
Jeffrey Jonas
Keyword(s):  
Climate Change ◽  
Solar Irradiance ◽  
Cloud Cover ◽  
Climate Models ◽  
Climate Model ◽  
Middle Atmosphere ◽  
Global Climate ◽  
Stratospheric Ozone ◽  
Model Simulations ◽  
The Impact

Abstract Simulations of the preindustrial and doubled CO2 climates are made with the GISS Global Climate Middle Atmosphere Model 3 using two different estimates of the absolute solar irradiance value: a higher value measured by solar radiometers in the 1990s and a lower value measured recently by the Solar Radiation and Climate Experiment. Each of the model simulations is adjusted to achieve global energy balance; without this adjustment the difference in irradiance produces a global temperature change of 0.4°C, comparable to the cooling estimated for the Maunder Minimum. The results indicate that by altering cloud cover the model properly compensates for the different absolute solar irradiance values on a global level when simulating both preindustrial and doubled CO2 climates. On a regional level, the preindustrial climate simulations and the patterns of change with doubled CO2 concentrations are again remarkably similar, but there are some differences. Using a higher absolute solar irradiance value and the requisite cloud cover affects the model’s depictions of high-latitude surface air temperature, sea level pressure, and stratospheric ozone, as well as tropical precipitation. In the climate change experiments it leads to an underestimation of North Atlantic warming, reduced precipitation in the tropical western Pacific, and smaller total ozone growth at high northern latitudes. Although significant, these differences are typically modest compared with the magnitude of the regional changes expected for doubled greenhouse gas concentrations. Nevertheless, the model simulations demonstrate that achieving the highest possible fidelity when simulating regional climate change requires that climate models use as input the most accurate (lower) solar irradiance value.

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