Page 38 - AJWEP-22-4

Qin, et al.

A B

Figure 1. Distribution of meteorological stations (A) and geographical location (B) in the study area
Note: The Arcgis10.8 software was used in this study. The map data were obtained from the China Standard Map
Service System. Drawing review No: GS(2020)4619.

2.2.1. Effective wind energy density (EWED) where Q is the total solar annual radiation (MJ·m ), R
−2
When the wind speed ranges from 3 to 20 m/s, the is the daily TSR (MJ·m ), S is the sunshine percentage,
−2
kinetic energy of the airflow per unit area and unit time and n is the ordinal number of days in a year. The daily
is referred to as the EWED. 10,18 The EWED is calculated TSR R is calculated using:
using the following formula:
R = I E (ω sinϕ sinδ+cosϕ sinω)⁄π (IV)
n
1 3 −2
W V i (I) where R is the daily TSR (MJ·m ), E is the average
8
2 n distance between the sun and Earth (1.4966 × 10 m), δ
i1
is the solar declination, Φ is the geographical latitude,
where W is the EWED (W/m ), ρ is the air density ω is the hour angle at sunset, I is the solar constant,
2
(kg/m ), V is the average wind speed (m/s), and n is the set to 1,367 W/m (118.109 MJ·m ·d ), and π is
3
−1
−2
2
total number of days when the average wind speed is the mathematical constant (3.14159). The sunshine
within the range of 3 – 20 m/s. percentage S is calculated as:
This study used daily average air pressure and daily
average temperature data from the dataset to calculate H (V)
the daily air density ρ at each site. The formula used is S 215/
as follows:
where H is the sunshine duration (hours), and ω is
P
(II) the hour angle at sunset.

RT
2.3. Research methods
In this equation, ρ is the daily air density (kg/m ), P 2.3.1. Analysis of change trend
3
is the daily average air pressure (Pa or N/m ), R is the The Mann–Kendall (MK) non-parametric test was
2
gas constant for air (287 J/[kg·K]), and T is the daily employed to assess long-term trends and detect abrupt
average temperature in Kelvin (°C + 273). shifts in environmental variables. This rank-based
methodology, which does not require the assumption of
2.2.2. TSR a normal distribution and is robust against outliers, has
Based on sunshine duration, this study adopted been extensively validated for hydroclimatic time series
the methods of Lv et al. to calculate the TSR and analysis. 20,21 Its computational reliability accounts for its
8
subsequently computed the annual average TSR using widespread application in identifying climate-induced
summation and averaging methods. 10,19 The formula is changes and system transitions in meteorological and
as follows: hydrological research. The formula is as follows:

n k i1
k
Q R S (III) S a k 23( , ,..., n) (VI)
ii
ij
i1 i1 i1

Volume 22 Issue 4 (2025) 30 doi: 10.36922/AJWEP025190147