pre-Download of QMwind in `add_griddap()` example so that example can run within CRAN Time limits
QMwindAn object of class griddap_nc (inherits from nc, data.frame) with 0 rows and 2 columns.
obtained using the `rerddap` command wind <- griddap('erdQMwindmday', time = c('2016-11-16', '2017-01-16'), latitude = c(30, 50), longitude = c(210, 240), fields = 'x_wind') )