scholarly journals The effects of clouds and aerosols on net ecosystem CO<sub>2</sub> exchange over semi-arid Loess Plateau of Northwest China

2010 ◽  
Vol 10 (17) ◽  
pp. 8205-8218 ◽  
Author(s):  
X. Jing ◽  
J. Huang ◽  
G. Wang ◽  
K. Higuchi ◽  
J. Bi ◽  
...  
Keyword(s):  
Solar Radiation ◽  
Northwest China ◽  
Co2 Uptake ◽  
Light Use Efficiency ◽  
Earth Surface ◽  
Clearness Index ◽  
The Earth ◽  
Use Efficiency ◽  
The Difference ◽  
Semi Arid

Abstract. The impacts of clouds and atmospheric aerosols on the terrestrial carbon cycle at semi-arid Loess Plateau in Northwest China are investigated, by using the observation data obtained at the SACOL (Semi-Arid Climate and Environment Observatory of Lanzhou University) site. Daytime (solar elevation angles of larger than 50°) net ecosystem exchange (NEE) of CO2 obtained during the midgrowing season (July–August) are analyzed with respect to variations in the diffuse radiation, cloud cover and aerosol optical depth (AOD). Results show a significant impact by clouds on the CO2 uptake by the grassland (with smaller LAI values) located in a semi-arid region, quite different from areas covered by forests and crops. The light saturation levels in the canopy are low, with a value of about 434.8 W m−2. Thus, under overcast conditions of optically thick clouds, the CO2 uptake increases with increasing clearness index (the ratio of global solar radiation received at the Earth surface to the extraterrestrial irradiance at a plane parallel to the Earth surface), and a maximum CO2 uptake and light use efficiency of vegetation occur with the clearness index of about 0.37 and lower air temperature. Under other sky conditions, CO2 uptake decreases with cloudiness but light use efficiency is enhanced, due to increased diffuse fraction of PAR. Additionally, under cloudy conditions, changes in the NEE of CO2 also result from the interactions of many environmental factors, especially the air temperature. In contrast to its response to changes in solar radiation, the carbon uptake shows a slightly negative response to increased AOD. The reason for the difference in the response of the semi-arid grassland from that of the forest and crop lands may be due to the difference in the canopy's architectural structure.

scholarly journals The effects of clouds and aerosols on net ecosystem CO<sub>2</sub> exchange over semi-arid Loess Plateau of Northwest China

2010 ◽  
Vol 10 (5) ◽  
pp. 13337-13372
Author(s):  
X. Jing ◽  
J. Huang ◽  
G. Wang ◽  
K. Higuchi ◽  
J. Bi ◽  
...  
Keyword(s):  
Loess Plateau ◽  
Air Temperature ◽  
Northwest China ◽  
Co2 Uptake ◽  
Observation Data ◽  
Light Use Efficiency ◽  
Clearness Index ◽  
Use Efficiency ◽  
The Difference ◽  
Semi Arid

Abstract. The impacts of clouds and atmospheric aerosols on the terrestrial carbon cycle at semi-arid Loess Plateau in Northwest China are investigated, by using the observation data obtained at the SACOL (Semi-Arid Climate and Environment Observatory of Lanzhou University) site. Daytime (solar elevation angles of larger than 50°) NEE of CO2 obtained during the midgrowing season (July–August) are analyzed with respect to variations in the diffuse radiation, cloud cover and aerosol optical depth (AOD). Results show a significant impact by clouds and aerosols on the CO2 uptake by the grassland (with smaller LAI values) located in a semi-arid region, quite different from areas covered by forests and crops. The light saturation levels in canopy are lower, with a value of about 434.8 W m−2. Thus, under overcast conditions of optically thick clouds, the CO2 uptake increases with increasing clearness index, and a maximum CO2 uptake and light use efficiency of vegetation occur with the clearness index of about 0.37 and lower air temperature. Under other sky conditions the CO2 uptake decreases with the cloudiness but the light use efficiency is enhanced, due to increase in the fraction of diffuse PAR. Additionally, under cloudy conditions, changes in the NEE of CO2 also result from the interactions of many environmental factors, especially the air temperature. In contrast to its response to changes in solar radiation, the carbon uptake shows a negative response to increased AOD. The reason for the difference in the response of the semi-arid grassland from that of the forest and crop lands may be due to the difference in the canopy's architectural structure.

scholarly journals Spatial–Temporal Evolution Characteristics and Influencing Factors of Agricultural Water Use Efficiency in Northwest China—Based on a Super-DEA Model and a Spatial Panel Econometric Model

Water ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 632
Author(s):  
Weinan Lu ◽  
Wenxin Liu ◽  
Mengyang Hou ◽  
Yuanjie Deng ◽  
Yue Deng ◽  
...  
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Water Resource ◽  
Arid Regions ◽  
Econometric Model ◽  
Northwest China ◽  
Agricultural Water ◽  
Agricultural Water Use ◽  
Use Efficiency ◽  
Semi Arid

Improving agricultural water use efficiency (AWUE) is an important way to solve the shortage of water resources in arid and semi-arid regions. This study used the Super-DEA (data envelopment analysis) to measure the AWUE of 52 cities in Northwest China from 2000 to 2018. Based on spatial and temporal perspectives, it applied Exploratory Spatial Data Analysis (ESDA) to explore the dynamic evolution and regional differences of AWUE. A spatial econometric model was then used to analyze the main factors that influence the AWUE in Northwest China. The results showed firstly that the overall AWUE in Northwest China from 2000 to 2018 presented a steady upward trend. However, only a few cities achieved effective agricultural water usage by 2018, and the differences among cities were obvious. Secondly, AWUE showed an obvious spatial autocorrelation in Northwest China and showed significant high–high and low–low agglomeration characteristics. Thirdly, economic growth, urbanization development, and effective irrigation have significant, positive effects on AWUE, while per capita water resource has a significant, negative influence. Finally, when improving the AWUE in arid and semi-arid regions, plans should be formulated according to local conditions. The results of this study can provide new ideas on the study of AWUE in arid and semi-arid regions and provide references for the formulation of regional agricultural water resource utilization policies as well.

scholarly journals Protective Netting Improves Leaf-level Photosynthetic Light Use Efficiency in ‘Honeycrisp’ Apple Under Heat Stress

HortScience ◽  
2018 ◽  
Vol 53 (10) ◽  
pp. 1416-1422 ◽  
Author(s):  
Giverson Mupambi ◽  
Stefano Musacchi ◽  
Sara Serra ◽  
Lee A. Kalcsits ◽  
Desmond R. Layne ◽  
...  
Keyword(s):  
Heat Stress ◽  
Solar Radiation ◽  
Leaf Gas Exchange ◽  
Growing Season ◽  
High Light ◽  
Weather Data ◽  
Light Use Efficiency ◽  
Ambient Temperatures ◽  
Leaf Level ◽  
Use Efficiency

Globally, apple production often occurs in semiarid climates characterized by high summer temperatures and solar radiation. Heat stress events occur regularly during the growing season in these regions. For example, in the semiarid eastern half of Washington State, historic weather data show that, on average, 33% of the days during the growing season exceed 30 °C. To mediate some of the effects of heat stress, protective netting (PN) can be used to reduce the occurrence of fruit sunburn. However, the impacts of reduced solar radiation in a high light environment on light-use efficiency and photosynthesis are poorly understood. We sought to understand the ecophysiological response of apple (Malus domestica Borkh. cv. Honeycrisp) under blue photoselective PN during days with low (26.6 °C), moderate (33.7 °C), or high (38.1 °C) ambient temperatures. Two treatments were evaluated; an uncovered control and blue photoselective PN. Maximum photochemical efficiency of PSII, or photosystem II (Fv/Fm) was significantly greater at all measurement times under blue photoselective PN compared with the control on days with high ambient temperatures. Fv/Fm dropped below 0.79, which is considered the threshold for stress, at 1000 hr in the control and at 1200 hr under blue photoselective PN on a day with high ambient temperature. On days with low or moderate ambient temperatures, Fv/Fm was significantly greater under blue photoselective PN at 1400 hr, which coincided with the peak in solar radiation. ‘Honeycrisp’ apple exhibited dynamic photoinhibition as shown by the diurnal decline in Fv/Fm. Quantum photosynthetic yield of PSII (ΦPSII) was also generally greater under blue photoselective PN compared with the control for days with moderate or high ambient temperatures. Photochemical reflectance index (ΔPRI), the difference in reflectance between a stress-responsive and nonstress-responsive wavelength, was greater under PN compared with the control on the day with high ambient temperatures, with no differences observed under low or moderate ambient temperatures. Leaf gas exchange did not show noticeable improvement under blue photoselective netting when compared with the control despite the improvement in leaf-level photosynthetic light use efficiency. In conclusion, PN reduced incoming solar radiation, improved leaf-level photosynthetic light use efficiency, and reduced the symptoms of photoinhibition in a high-light, arid environment.

Modeling Solar Radiation at the Earth Surface

2012 ◽  
pp. 127-179 ◽  
Author(s):  
Marius Paulescu ◽  
Eugenia Paulescu ◽  
Paul Gravila ◽  
Viorel Badescu
Keyword(s):  
Solar Radiation ◽  
Earth Surface ◽  
The Earth

Estimating photosynthetic light-use efficiency using the photochemical reflectance index: variations among species

2004 ◽  
Vol 31 (3) ◽  
pp. 255 ◽  
Author(s):  
Jianmin Guo ◽  
Craig M. Trotter
Keyword(s):  
Light Response ◽  
Species Group ◽  
Photosynthetic Parameters ◽  
Co2 Uptake ◽  
Light Use Efficiency ◽  
Photochemical Reflectance Index ◽  
Response Data ◽  
Use Efficiency ◽  
Species Specific ◽  
The Relationship

Recent studies have shown that the photochemical reflectance index (PRI), derived from narrow waveband reflectance at 531 and 570 nm, can be used as a remote measure of photosynthetic light-use efficiency (LUE). However, uncertainty remains as to the consistency of the relationship between PRI and LUE across species. In this study we examined the relationship between the PRI and various photosynthetic parameters for a group of species with varying photosynthetic capacity. At constant irradiance, for the species group as a whole, the PRI was well correlated with LUE (r2=0.58) and with several other photosynthetic parameters, but best correlated with the ratio of carotenoids to chlorophylls contents (Caro / Chl). Despite the interspecific trends observed, determination of light response functions for the PRI in relation to photosynthetic parameters revealed that species-specific relationships were clearly stronger. For example, r2>0.90 for species-level PRI / LUE relationships. Also, the species-specific light-response data show that the magnitude of the PRI can be related to the magnitude of the saturated irradiance and the rate of CO2 uptake. As demonstrated here, a light response function provides a simple yet precise approach for characterising the relationship between the PRI and photosynthetic parameters, which should assist with improved evaluation of the usefulness of the PRI as a generalised measure of LUE.

scholarly journals Modeling light use efficiency in a subtropical mangrove forest equipped with CO<sub>2</sub> eddy covariance

2013 ◽  
Vol 10 (3) ◽  
pp. 2145-2158 ◽  
Author(s):  
J. G. Barr ◽  
V. Engel ◽  
J. D. Fuentes ◽  
D. O. Fuller ◽  
H. Kwon
Keyword(s):  
Eddy Covariance ◽  
Environmental Conditions ◽  
Mangrove Forest ◽  
Environmental Drivers ◽  
Model Parameters ◽  
Co2 Uptake ◽  
Light Use Efficiency ◽  
Co2 Fluxes ◽  
Use Efficiency ◽  
Reflectance Data

Abstract. Despite the importance of mangrove ecosystems in the global carbon budget, the relationships between environmental drivers and carbon dynamics in these forests remain poorly understood. This limited understanding is partly a result of the challenges associated with in situ flux studies. Tower-based CO2 eddy covariance (EC) systems are installed in only a few mangrove forests worldwide, and the longest EC record from the Florida Everglades contains less than 9 years of observations. A primary goal of the present study was to develop a methodology to estimate canopy-scale photosynthetic light use efficiency in this forest. These tower-based observations represent a basis for associating CO2 fluxes with canopy light use properties, and thus provide the means for utilizing satellite-based reflectance data for larger scale investigations. We present a model for mangrove canopy light use efficiency utilizing the enhanced green vegetation index (EVI) derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) that is capable of predicting changes in mangrove forest CO2 fluxes caused by a hurricane disturbance and changes in regional environmental conditions, including temperature and salinity. Model parameters are solved for in a Bayesian framework. The model structure requires estimates of ecosystem respiration (RE), and we present the first ever tower-based estimates of mangrove forest RE derived from nighttime CO2 fluxes. Our investigation is also the first to show the effects of salinity on mangrove forest CO2 uptake, which declines 5% per each 10 parts per thousand (ppt) increase in salinity. Light use efficiency in this forest declines with increasing daily photosynthetic active radiation, which is an important departure from the assumption of constant light use efficiency typically applied in satellite-driven models. The model developed here provides a framework for estimating CO2 uptake by these forests from reflectance data and information about environmental conditions.

scholarly journals Direct effect of aerosols on solar radiation and gross primary production in boreal and hemiboreal forests

2018 ◽  
Vol 18 (24) ◽  
pp. 17863-17881 ◽  
Author(s):  
Ekaterina Ezhova ◽  
Ilona Ylivinkka ◽  
Joel Kuusk ◽  
Kaupo Komsaare ◽  
Marko Vana ◽  
...  
Keyword(s):  
Solar Radiation ◽  
Primary Production ◽  
Direct Effect ◽  
Gross Primary Production ◽  
Global Radiation ◽  
Diffuse Radiation ◽  
Light Use Efficiency ◽  
Diffuse Fraction ◽  
Aerosol Loading ◽  
Use Efficiency

Abstract. The effect of aerosol loading on solar radiation and the subsequent effect on photosynthesis is a relevant question for estimating climate feedback mechanisms. This effect is quantified in the present study using ground-based measurements from five remote sites in boreal and hemiboreal (coniferous and mixed) forests of Eurasia. The diffuse fraction of global radiation associated with the direct effect of aerosols, i.e. excluding the effect of clouds, increases with an increase in the aerosol loading. The increase in the diffuse fraction of global radiation from approximately 0.11 on days characterized by low aerosol loading to 0.2–0.27 on days with relatively high aerosol loading leads to an increase in gross primary production (GPP) between 6 % and 14 % at all sites. The largest increase in GPP (relative to days with low aerosol loading) is observed for two types of ecosystems: a coniferous forest at high latitudes and a mixed forest at the middle latitudes. For the former ecosystem the change in GPP due to the relatively large increase in the diffuse radiation is compensated for by the moderate increase in the light use efficiency. For the latter ecosystem, the increase in the diffuse radiation is smaller for the same aerosol loading, but the smaller change in GPP due to this relationship between radiation and aerosol loading is compensated for by the higher increase in the light use efficiency. The dependence of GPP on the diffuse fraction of solar radiation has a weakly pronounced maximum related to clouds.

Changes in Irradiance and Illuminance on Earth Surface during 11-Year Solar Activity Cycle

2020 ◽  
pp. 61-66
Author(s):  
Alexander V. Leonidov
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Solar Radiation ◽  
Visible Region ◽  
Earth Surface ◽  
Solar Cycles ◽  
Spectral Window ◽  
Solar Altitude ◽  
The Earth ◽  
Analytic Expression

The article formulates the analytic expression approximating the sequence of Gregorian 11-year solar cycles and the expression of solar activity within one cycle. The dependences of effective thermodynamic temperature of the Sun photosphere and the solar constant, and the solar illuminance constant at the upper border of Earth atmosphere on the year number within one solar cycle were obtained. The generalised analytic expression for integral transmittance of atmosphere (within its spectral window) on the Earth surface for the direct and diffuse components of solar radiation and their sums at different solar altitude angles is presented. The analytic expressions of dependences of irradiance and illuminance on the Earth surface within spectral window of atmosphere and within the visible region of solar radiation spectrum on the year number within a certain solar cycle at different solar altitude angles are obtained. The results of calculation of direct and diffuse components of irradiance and illuminance and their sums in the case of clear sky are presented for example. The proposed approach allows similar calculations to conduct for different types of sky cover.

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