Year	mm per year
1961	1577
1962	1577
1963	1577
1964	1577
1965	1577
1966	1577
1967	1577
1968	1577
1969	1577
1970	1577
1971	1577
1972	1577
1973	1577
1974	1577
1975	1577
1976	1577
1977	1577
1978	1577
1979	1577
1980	1577
1981	1577
1982	1577
1983	1577
1984	1577
1985	1577
1986	1577
1987	1577
1988	1577
1989	1577
1990	1577
1991	1577
1992	1577
1993	1577
1994	1577
1995	1577
1996	1577
1997	1577
1998	1577
1999	1577
2000	1577
2001	1577
2002	1577
2003	1577
2004	1577
2005	1577
2006	1577
2007	1577
2008	1577
2009	1577
2010	1577
2011	1577
2012	1577
2013	1577
2014	1577
2015	1577
2016	1577
2017	1577
2018	1577
2019	1577
2020	1577