Simulate occluded particle systems in Unity 3D.

Blizzard.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Blizzard : MonoBehaviour {
    public float verticleCeiling = 100;
    public ParticleSystem[] blizzardEmitters;

	// Use this for initialization
	void Start () {
		
	}
	
	// Update is called once per frame
	void Update () {
	    foreach (var particleSystem in blizzardEmitters)
	    {
            Ray ray = new Ray(particleSystem.transform.position + Vector3.up * verticleCeiling, Vector3.down);
            RaycastHit hit;
	        if (Physics.Raycast(ray, out hit, verticleCeiling))
	        {
                particleSystem.enableEmission = false;
	        }
	        else
	        {
                particleSystem.enableEmission = true;
	        }
	    }
	}

    void OnDrawGizmos()
    {
        Gizmos.color = Color.red;
        foreach (var particleSystem in blizzardEmitters)
        {
            Gizmos.DrawRay(particleSystem.transform.position + Vector3.up*verticleCeiling, Vector3.down);
        }
    }
}