图解 gma 气候标准化指数运算过程的数组变化流程：以 SPI 为例

目标

【gma 计算 SPI 指数过程中的数据变化】

环境

系统： Window 10+ (X64)
Python 版本： 3.8.8 +
gma 版本： 1.1.0 +

  gma：地理与气象分析库。安装和详细功能帮助见：地理与气象分析库。

数据与函数

import gma

gma 气象与气候模块（gma.climet）目前包含两个标准化指数：SPI 和 SPEI。以 SPI 为例，其参数帮助如下：

help(gma.climet.SPI)

Help on function SPI in module gma.climet:

SPI(PRE, Axis=None, Scale=1, Periodicity=12, Distribution='Gamma')
    Calculate the Standardized Precipitation Index.
    
    Parameters
    ----------
    PRE: array. 
        Precipitation (mm).
    
    **Optional
    ----------
    Axis = int. Default None. 
        Calculation axis. If not set (None), multidimensional data will be expanded to 1 dimension for calculation.
    
    Scale = int. Default 1.
        Time scale. For example: 1, 3 or others.
    
    Periodicity = int. Default 12. 
        Periodicity of data. For example: the monthly scale can have a period of 12.
        
    Distribution = str. Default 'Gamma'.
        Distribution type to be used for the internal fitting/transform computation.
        Supported distributions include: 
    
            'Gamma'(Maximum Likelihood Estimation), 
            
            'LogLogistic'(L-Moment Estimation(PWD)),
            
            'Pearson3'(L-Moment Estimation).
    
    *Note: Scale, Periodicity are based on calculated axis!
    
    Returns
    ----------
    Type: array.
    
    References
    ----------
    McKee T B, Doesken N J, Kleis J. The relationship of drought frequency and duration to time scales[R]. 
    Eighth Conf. on Applied Climatology, Anaheim, CA: American Meteor Society, 1993.

注意：Distribution 参数自 1.1.1 版本引入。SPI 默认 ‘Gamma’ 分布。

计算 SPI

import gma
# 以 Axis = 1 轴，周期为6，（时间尺度默认为 1），计算SPI
SPI = gma.climet.SPI(PRE, Axis = 1, Periodicity = 6)

数组变化过程