make use of slurm arrrays

map date range to slurm task ids, .e.g.

```
sbatch --export=SLURM_ARRAY_DATE_1='1979-01-01',SLURM_ARRAY_DATE_2='1979-01-02' --array=1,2 array.py
```

with `array.py`

```python
#!/usr/bin/env python
import os

task_id = os.environ['SLURM_ARRAY_TASK_ID']
task_input = os.environ[f'SLURM_ARRAY_DATE_{task_id}']

print(task_id, task_input)
```