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"""
Adds a new observation field to weewx: [sunshine_hours]
If the radiation observed during an interval of time exceeds 120 W/m2, then the interval is considered sunny,
and [sunshine_hours] is set the length of the time interval.
When [sunshine_hours] is summed over a day, the result is the number of hours during the day when radiation
exceeded 120 W/m2, or 'hours of sunshine'.
The threshold of 120 W/m2 can be overwritten in weewx.conf:
[RadiationDays]
min_sunshine = 120
Installation:
1. Save this file to your user customisations directory (which is often /usr/share/weewx/user)
2. Enable this service in weewx.conf by adding user.radiationhours.RadiationHours to the process_services list.
[Engine]
[[Services]]
# This section specifies the services that should be run. They are
# grouped by type, and the order of services within each group
# determines the order in which the services will be run.
prep_services = weewx.engine.StdTimeSynch
process_services = user.radiationhours.RadiationHours, weewx.engine.StdConvert, weewx.engine.StdCalibrate, weewx.engine.StdQC, weewx.wxservices.StdWXCalculate
3. Add [sunshine_hours] to the database schema so tables include this new observation field.
In weewx.conf, change the wx_binding schema from schemas.wview.schema to user.radiationhours.schema_with_sunshine_hour
[DataBindings]
[[wx_binding]]
# The database must match one of the sections in [Databases].
# This is likely to be the only option you would want to change.
database = archive_sqlite
# The name of the table within the database
table_name = archive
# The manager handles aggregation of data for historical summaries
manager = weewx.wxmanager.WXDaySummaryManager
# The schema defines the structure of the database.
# It is *only* used when the database is created.
#schema = schemas.wview.schema
schema = user.radiationhours.schema_with_sunshine_hour
4. Shutdown Weewx and update your database to bring in the new field.
wee_database weewx.conf --reconfigure
Make sure you know what you're doing at this point, you can potentially corrupt/lose your archive data.
The weewx customization guide covers this in a lot more detail.
5. Tell Weewx about the units for this new type
Add this to user/extensions.py:
#
# Units for sunshine_days calculated field
#
import weewx.units
weewx.units.obs_group_dict['sunshine_hours'] = 'group_radiation'
I've cheated here since Weewx doesn't have a unit for hours. So any graphs of sunshine hours will have the
units W/m2, which I have hidden on the graph by setting the colour of the unit text to the background colour
of the graph.
6. Use [sunshine_hours] in your graphs and html template tags.
Lots more detail on this process can be found here:
http://www.weewx.com/docs/customizing.htm#Adding_a_new_observation_type
"""
import syslog
import weewx
from weewx.wxengine import StdService
class RadiationHours(StdService):
def __init__(self, engine, config_dict):
# Pass the initialization information on to my superclass:
super(RadiationHours, self).__init__(engine, config_dict)
# Default threshold value is 120 W/m2
self.min_sunshine = 120.0
if 'RadiationDays' in config_dict:
self.min_sunshine = float(config_dict['RadiationDays'].get('min_sunshine', self.min_sunshine))
# Start intercepting events:
self.bind(weewx.NEW_ARCHIVE_RECORD, self.newArchiveRecord)
def newArchiveRecord(self, event):
"""Gets called on a new archive record event."""
radiation = event.record.get('radiation')
if (radiation is not None) and (radiation > self.min_sunshine):
event.record['sunshine_hours'] = event.record['interval'] / 60.0
else:
event.record['sunshine_hours'] = 0.0
syslog.syslog(syslog.LOG_DEBUG, "Calculated sunshine_hours = %f, based on radiation = %f, and min_sunshine = %f" %
(event.record['sunshine_hours'], radiation, self.min_sunshine))
import schemas.wview
schema_with_sunshine_hours = schemas.wview.schema + [('sunshine_hours', 'REAL')]