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Based on data from the Gurbantunggut Desert, the largest fixed/semi-fixed desert in China, and ERA5-Land reanalysis data, the long-term variations and spatial surface heat source (SHS) differences in the Gurbantunggut Desert are discussed herein. The results show the following: (1) The hourly SHS at the Kelameili station during the 2013–2021 period was a weak heat source at night; contrastingly, it was a strong heat source during the day. The duration of the hourly SHS increased gradually from January to July, but it decreased gradually from July to December. The daily SHS showed obvious seasonal variation, reaching the maximum in summer and the minimum in winter. The ERA5-Land reanalysis can reproduce all the variation characteristics of the SHS well. (2) The climatology (i.e., multi-year mean) of the monthly SHS intensity was lower than 50 W/m2 during the January–March and September–December periods in the Gurbantunggut Desert, indicating a weak heat source. On the other hand, the climatology recorded in April–August was higher than 50 W/m2, with a strong heat source. From the perspective of spatial distribution, the eastern and western regions of the Gurbantunggut Desert show strong heat sources, while the central region shows weak heat sources. The spatial distribution of the first and second modes of the empirical orthogonal function (EOF) decomposition reflected the consistent spatial variability and a north–south (or east–west) polarity variation of the monthly SHS in the Gurbantunggut Desert, respectively. (3) The yearly SHS showed negative anomalies during the 1950–1954, 1964–1982 and 2004–2015 periods, and positive anomalies during the 1955–1963, 1983–2003 and 2016–2021 periods in the Gurbantunggut Desert. Additionally, the time series of the SHS anomalies was positively correlated with the Interdecadal Pacific Oscillation (IPO) index. During the negative IPO phase, the yearly SHS showed a negative anomaly in the Gurbantunggut Desert, while the yearly SHS showed a positive anomaly during the positive IPO phase in most regions of the Gurbantunggut Desert. [ABSTRACT FROM AUTHOR]

The exchange of energy between the land surface and atmosphere is dependent upon crucial parameters, including surface roughness, emissivity, bulk transfer coefficients for momentum (CD) and heat (CH). These parameters are calculated through site observation data and remote sensing data. The following conclusions are drawn: (1) the aerodynamic roughness of the Gurbantunggut Desert measures 1.1 × 10−2 m, which is influenced by the varying conditions of the underlying surface. The roughness decreases as wind speed increases and is seen to be directly proportional to the growth of vegetation. From April to June, the aerodynamic roughness increases with increasing vegetation cover, but begins to gradually decrease after July. Spatially, the middle regions show higher roughness values than the eastern and western areas. In the central part of the desert, the roughness is between 2.37 × 10−2 m and 2.46 × 10−2 m from April to November. The northwest and northeast regions measure 1.41 × 10−2 m–2.04 × 10−2 m and 1.53 × 10−2 m–2.39 × 10−2 m, respectively. (2) The surface emissivity is 0.93, and it varies depending on the snow and vegetation present in the underlying area. (3) CD and CH exhibit an inverse relationship with wind speed. When wind speed falls below 6 m/s, the CD declines rapidly as wind speed increases. In contrast, once wind speed surpasses 6 m/s, the propensity for the CD to decrease with increasing wind speed slows down and approaches stability. [ABSTRACT FROM AUTHOR]

• Vortex-related data using continuous observations at Kelameili Station in the Gurbantunggut Desert. • The correlation analysis of NEE, GPP, Reco and various environmental factors was carried out. • Assess the carbon sequestration capacity of China's second largest desert and largest fixed semi-fixed desert (Gurbantunggut Desert). • The comparison of carbon source/sink functions in different terrestrial ecosystems provides a reference. • a new direction for finding "carbon failures". Although previous studies have illustrated the variation of CO 2 fluxes in different terrestrial ecosystems, more needs to be reported on desert ecosystems. This study, based on the eddy covariance (EC) measurements data over the Gurbantunggut Desert, analyzed the controlling factors and variations of net ecosystem exchange (NEE), gross primary production (GPP), and ecosystem respiration (Reco) during the growing season (April-September2021) in Gurbantunggut Desert. The results were as follows: 1) Carbon fluxes in the Gurbantunggut Desert had prominent daily and seasonal variations during the growing season. On the daily scale, it showed a net uptake during the day and a net release at night, and the monthly average daily change curve of NEE was "U" shaped; on the seasonal scale, carbon uptake was observed in all months, with a peak of −37.76 gC m−2 month−1 in May. 2)The cumulative amounts of NEE, GPP, and Reco in the Gurbantunggut Desert were −193.74, 235.43, and 41.69 g C m−2, respectively, throughout the growing season, showing carbon sinks. 3) Correlation analysis with environmental factors revealed that NEE, GPP, and Reco of desert ecosystems were highly significantly correlated with photosynthetically active radiation (PAR) at different time scales (p < 0.01). Second, at the half-hourly scale, all environmental factors showed vital significance, with a high correlation with air temperature (Tair) and soil temperature (Tsoil); at the monthly scale, they were significantly correlated with Precipitation (p < 0.05). 4) Photosynthetically active radiation is the dominant factor affecting the daily net ecosystem carbon exchange rate. The two are consistent with the rectangle hyperbola model where the daily net ecosystem carbon exchange rate decreases with increasing photosynthetically active radiation. The results indicate that carbon fluxes in the growing season of the Gurbantunggut Desert ecosystem are more sensitive to the response of photosynthetically active radiation. The results have significant reference value for further understanding and research in predicting the source-sink function and influence mechanism of desert ecosystems. [ABSTRACT FROM AUTHOR]