Increase in Surface Friction Dominates the Observed Surface Wind Speed Decline during 1973–2014 in the Northern Hemisphere Lands

2019 ◽  
Vol 32 (21) ◽  
pp. 7421-7435 ◽  
Author(s):  
Zhengtai Zhang ◽  
Kaicun Wang ◽  
Deliang Chen ◽  
Jianping Li ◽  
Robert Dickinson
Keyword(s):  
Wind Speed ◽  
Atmospheric Circulation ◽  
Influencing Factors ◽  
Northern Hemisphere ◽  
Surface Wind ◽  
Surface Friction ◽  
Surface Wind Speed ◽  
Urbanization Effect ◽  
Turbulent Friction ◽  
Novel Approach

Abstract During 1973–2014, a reduction trend in the observed surface wind speed (10 m) in the Northern Hemisphere lands has been widely reported; this reduction is referred to as “global stilling.” The primary determining factors of global stilling include atmospheric circulation, turbulent friction, and surface friction when ignoring the vertical influencing factors. Most of the existing studies on the attribution of global stilling do not take changing surface friction into account. In addition, there are other changes in the climate system, such as aerosol loading, which could have an impact on atmospheric circulation, but are not included in the majority of current models either. Here, we developed a novel approach based on modeled winds calculated from sea level pressure observations and applied the method to approximately 4000 weather stations in the Northern Hemisphere lands from 1973 to 2014 to attribute the stilling in the three factors. In our methods, we neglected the vertical influencing factors on surface wind speed but took the aerosols’ changes on atmospheric circulation and gradual urbanization effect on surface wind speed into account. We found that atmospheric circulation has dictated the monthly variation in surface wind speed during the past four decades. However, the increased surface friction dominates the long-term declining trend of wind stilling. Our studies had uncertainties while neglecting the influence of vertical factors on surface wind stilling, despite most of the existing studies showing their effect was minor compared to the three factors explored in our study.

scholarly journals Evaluation of Northern Hemisphere surface wind speed and wind power density in multiple reanalysis datasets

Energy ◽  
2020 ◽  
Vol 200 ◽  
pp. 117382 ◽  
Author(s):  
Haozeyu Miao ◽  
Danhong Dong ◽  
Gang Huang ◽  
Kaiming Hu ◽  
Qun Tian ◽  
...  
Keyword(s):  
Wind Speed ◽  
Wind Power ◽  
Power Density ◽  
Northern Hemisphere ◽  
Surface Wind ◽  
Surface Wind Speed ◽  
Wind Power Density ◽  
Hemisphere Surface

Global Near-Surface Wind Speed Changes over the Last Decades Revealed by Reanalyses and CMIP6 Model Simulations

2020 ◽  
pp. 1-53
Author(s):  
Kaiqiang Deng ◽  
Cesar Azorin-Molina ◽  
Lorenzo Minola ◽  
Gangfeng Zhang ◽  
Deliang Chen
Keyword(s):  
Wind Speed ◽  
Atmospheric Circulation ◽  
Decadal Variability ◽  
Surface Wind ◽  
Coupled Model ◽  
Surface Wind Speed ◽  
Hadley Cell ◽  
Near Surface ◽  
Model Simulations ◽  
Hydrological Cycles

AbstractNear-surface (10 m) wind speed (NWS) plays a crucial role in e.g. hydrological cycles, wind energy production and air pollution, but what drives their multi-decadal changes is still unclear. Using reanalysis datasets and Coupled Model Inter-comparison Projection Phase 6 (CMIP6) model simulations, this study investigates recent trends in the annual mean NWS. The results show that the northern hemisphere (NH) terrestrial NWS experienced significant (p<0.1) decreasing trends during 1980–2010, when the southern hemisphere (SH) ocean NWS was characterized by significant (p<0.1) upward trends. However, during 2010–2019, global NWS trends shifted in their sign: NWS trends over the NH land became positive, and trends over the SH tended to be negative. We propose that the strengthening of SH NWS during 1980–2010 was associated with intensified Hadley cell over the SH, while the declining of NH land NWS could have been caused by changes in atmospheric circulation, alteration of vegetation/land-use and the accelerating Arctic warming. The CMIP6 model simulations further demonstrate that the greenhouse gas (GHG) warming plays an important role in triggering the NWS trends over the two hemispheres during 1980–2010 through modulating meridional atmospheric circulation. This study also points at the importance of anthropogenic GHG forcing and the natural Pacific Decadal Oscillation to the long-term trends and multi-decadal variability in global NWS, respectively.

Understanding Atypical Midlevel Wind Speed Maxima in Hurricane Eyewalls

2020 ◽  
Vol 77 (5) ◽  
pp. 1531-1557 ◽  
Author(s):  
Daniel P. Stern ◽  
Jeffrey D. Kepert ◽  
George H. Bryan ◽  
James D. Doyle
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Surface Wind ◽  
Local Maximum ◽  
Surface Friction ◽  
Surface Wind Speed ◽  
Small Radius ◽  
Inertial Oscillation ◽  
Tangential Wind ◽  
Wind Speed Maximum

Abstract In tropical cyclones (TCs), the peak wind speed is typically found near the top of the boundary layer (approximately 0.5–1 km). Recently, it was shown that in a few observed TCs, the wind speed within the eyewall can increase with height within the midtroposphere, resulting in a secondary local maximum at 4–5 km. This study presents additional evidence of such an atypical structure, using dropsonde and Doppler radar observations from Hurricane Patricia (2015). Near peak intensity, Patricia exhibited an absolute wind speed maximum at 5–6-km height, along with a weaker boundary layer maximum. Idealized simulations and a diagnostic boundary layer model are used to investigate the dynamics that result in these atypical wind profiles, which only occur in TCs that are very intense (surface wind speed &gt; 50 m s−1) and/or very small (radius of maximum winds &lt; 20 km). The existence of multiple maxima in wind speed is a consequence of an inertial oscillation that is driven ultimately by surface friction. The vertical oscillation in the radial velocity results in a series of unbalanced tangential wind jets, whose magnitude and structure can manifest as a midlevel wind speed maximum. The wavelength of the inertial oscillation increases with vertical mixing length l∞ in a turbulence parameterization, and no midlevel wind speed maximum occurs when l∞ is large. Consistent with theory, the wavelength in the simulations scales with (2K/I)1/2, where K is the (vertical) turbulent diffusivity, and I2 is the inertial stability. This scaling is used to explain why only small and/or strong TCs exhibit midlevel wind speed maxima.

scholarly journals Contribution of variations in Northern Hemisphere annular mode to the near-surface wind speed changes over Eastern China for 1979-2017

2021 ◽  
Author(s):  
Jinlin Zha ◽  
Cheng Shen ◽  
Jian Wu ◽  
Deming Zhao ◽  
Cesar Azorin-Molina
Keyword(s):  
Wind Speed ◽  
Temperature Gradient ◽  
Northern Hemisphere ◽  
Air Temperature ◽  
Eastern China ◽  
Surface Wind ◽  
Surface Wind Speed ◽  
Near Surface ◽  
Annular Mode ◽  
Northern Hemisphere Annular Mode

Abstract Studies have shown that large-scale ocean-atmosphere circulations (LOACs) played the major role to the near-surface wind speed (NWS) changes over China; however, the mechanisms whereby LOACs influences NWS to have received little attention. In this study, the processes of the Northern Hemisphere annular mode (NAM) influencing the NWS changes are revealed over eastern China for 1979–2017. The results showed a slowdown in NWS, at a rate of − 0.09 ± 0.01 m s− 1 decade− 1; meanwhile, this decline could be partly driven by the weakening of the zonal wind component. When the NAM exhibits positive phases, the zonal-mean westerly weakens at the low-to-mid-latitudes (10°–40°N); meanwhile, in the troposphere descending flows prevail near 40°N and ascending flows prevail near 65°N, and in the lower troposphere there are northerly anomalies at the low-to-mid-latitudes and southerly anomalies at mid-to-high latitudes (40°–70°N). The anomalous meridional flows transport heat from lower latitudes to higher latitudes and weaken the north–south air temperature gradient. The decreased air temperature gradient over East Asia reduces the pressure-gradient near the surface in eastern China, thereby decreasing the NWS. Furthermore, the effects of NAM on NWS changes are more significant at interannual scale than decadal scale. 32.0 ± 15.8 % of the changes in the annual mean NWS are caused by the variations in NAM; meanwhile, the NAM contribution to the interannual changes in the zonal component of NWS reach 45.0 ± 12.9 %.

Recurrence Characteristics Analysis of Near-Surface Wind Speed Signal with Different Sampling Frequencies

2014 ◽  
Vol 599-601 ◽  
pp. 1605-1609 ◽  
Author(s):  
Ming Zeng ◽  
Zhan Xie Wu ◽  
Qing Hao Meng ◽  
Jing Hai Li ◽  
Shu Gen Ma
Keyword(s):  
Wind Speed ◽  
Surface Wind ◽  
Surface Wind Speed ◽  
Recurrence Plot ◽  
Sampling Frequency ◽  
Near Surface ◽  
Gas Leakage ◽  
Time Period ◽  
Characteristics Analysis ◽  
Quantification Analysis

The wind is the main factor to influence the propagation of gas in the atmosphere. Therefore, the wind signal obtained by anemometer will provide us valuable clues for searching gas leakage sources. In this paper, the Recurrence Plot (RP) and Recurrence Quantification Analysis (RQA) are applied to analyze the influence of recurrence characteristics of the wind speed time series under the condition of the same place, the same time period and with the sampling frequency of 1hz, 2hz, 4.2hz, 5hz, 8.3hz, 12.5hz and 16.7hz respectively. Research results show that when the sampling frequency is higher than 5hz, the trends of recurrence nature of different groups are basically unchanged. However, when the sampling frequency is set below 5hz, the original trend of recurrence nature is destroyed, because the recurrence characteristic curves obtained using different sampling frequencies appear cross or overlapping phenomena. The above results indicate that the anemometer will not be able to fully capture the detailed information in wind field when its sampling frequency is lower than 5hz. The recurrence characteristics analysis of the wind speed signals provides an important basis for the optimal selection of anemometer.

Ocean surface wind speed retrieval from C-band quad-polarized SAR measurements at optimal spatial resolution

2020 ◽  
Vol 12 (2) ◽  
pp. 155-164
Author(s):  
He Fang ◽  
William Perrie ◽  
Gaofeng Fan ◽  
Tao Xie ◽  
Jingsong Yang
Keyword(s):  
Wind Speed ◽  
Spatial Resolution ◽  
Surface Wind ◽  
Ocean Surface ◽  
Surface Wind Speed ◽  
Ocean Surface Wind
Sign in / Sign up

Export Citation Format

Share Document