sinaica_station_dates() and
sinaica_param_data() return NULL when SINAICA is downsinaica_param_data() and
sinaica_station_data() to download air quality datasinaica_station_dates() and
sinaica_station_params() to query station metadatastations_sinaica and
params_sinaicaNEWS.md file to track changes to the
package.